Here's another image of the backyard!
Thanks again for reading!

and lastly the front yard as well!

You have attributed many effects to many causes. Almost none of those causes caused your lawn to be like this. For example applying herbicide with temps in the 70s is ideal. The weeds are there because you seeded in the spring instead of fall. Summer weed seeds are sprouting in the spring and you watered them perfectly along with your grass seed.

I don't see any crabgrass. Crabgrass grows low to the ground.

It appears the soil mounds up between the bricks and the fence. Is it higher in the middle than at the bricks? If so you might consider having all that excess soil removed so that the water all drains off the brick and down across the grass. Or is the soil still higher on the other side of the fence and this is all sloping one direction?

In your area fall begins in August. That is the time to start renovations or even just overseeding.

I cringe when I watch "This Old House," and they talk about yards. Stick to the houses, guys! Having said that, slit seeders are great. You should be able to find one.

Before getting too specific about solutions, it would help to know a little more.

What is your watering regimen? How often do you water and for how long?

How high/low do you mow?

What products have you applied to the lawn since you moved in?

Thank you so much for your reply!

In terms of our backyard, its hard to tell from the pictures, but the backyard actually slopes toward the middle and downhill -- its like a funnel-- not ideal for yard games, but the water does run pretty steadily into the wood behind our house. All that being said, our yard is pretty bumpy and uneven. (I've attached a new picture a bit less zoomed in)

We've probably been watering once to twice a week for maybe 10-15 minutes. That was mainly in the areas with newer lawn, not necessarily the entire yard, although i did water the entire lawn a few weeks ago when we lacked rain.

And I believe the mower is set at about 3 inches.

And the products we've used have been:
- Scotts Weed and Feed
-Scotts North East Blend Grass Seed
-Expert Gardener Lawn Fertilizer
-Bayer Advanced Complete Insect Killer

Good answers, thanks. I'm sometimes hesitant to get into detail before I know if there are any special circumstances to be aware of.

Here is some general lawn care advice I've learned after reading here and other forums over 12 years. This was not what I believed when I first got here. This is the accumulated advice of hundreds or thousands of peoples' experience.

Watering
Water deeply and infrequently. Deeply means one inch all at one time. Infrequently means no more than once a week when temps are in the 90s and once every 2 weeks when temps are in the 80s. This seems to work in Phoenix and in New Orleans. Of course in New Orleans they can count on rain for all their watering. YOUR grass might need to be weaned into deep and infrequent watering. Start by figuring out how long it takes your sprinkler to put out an inch of water. My oscillator sprinkler with my water pressure takes 8 full hours to get an inch. My neighbor's high flow, in ground system takes 20 minutes. You'll have to figure it out for your set of hoses, sprinklers, and water pressure. Put some tuna or cat food cans out in the yard and turn on the sprinkler. Time how long it takes to fill the cans. That is your target watering time from now on. Every time you water, use that time. Once you do that, start your calendar. Watch the grass (not the weeds) for signs of wilting. When you see the grass turn color to a darker green or the blades folding together, then water for your target time. Restart your calendar. When you water like this several things happen. One is the grass roots will extend and grow deeper into the soil to get the water deeper down. Two is the surface of the soil will dry out completely before you water again. That means new weed seeds will not germinate (they need continual surface moisture). Three is that certain weeds which require continual surface moisture will die out.

Mowing
Mulch mow at your mower's highest setting or one notch lower. Sounds like you're doing that. But mow once a week. Grass will become stressed if you mow more than 1/3 of the length of the blade off, so weekly mowing is recommended if the grass is growing. Sometimes in summer, if you get a hot spell, you can let the grass go for several weeks. Longer grass needs less water. But when you mow it back, watch for that stress from mowing more than 1/3 off.

Fertilizer
In your area you should fertilize once in the late spring. Memorial Day is an easy day to remember. If you fertilize when the Scott's commercials come on in March, you will over stimulate the grass resulting in a crash as the grass uses up all the sugar reserves in the roots. The grass will naturally come in at high speed in the spring, so you don't need to do anything until after that fast growth stops. Then the grass needs two more doses of fertilizer in the fall. Labor Day and Thanksgiving are easy days to remember for those. The last app should go down after the grass stops growing in the late fall. Thanksgiving is just a guideline, not a rule.

Seeding
For northern lawns the best time to seed new grass is in the early fall. Your early fall is August. That gives you time to evaluate the new grass and reseed if you get some thin spots. Fescue grasses will grow down in your little glen in the shade. Both fescue and Kentucky bluegrass will grow in full sun. Many people like the fescue for remaining green all winter, but fescue tends to thin out over the year(s) allowing weeds in. Kentucky bluegrass will turn brown in the winter, but it grows a dense carpet of grass and does not require annual reseeding. You can mix the two grasses if you like. I can't give you specific seed selection advice other than to say you get what you pay for in seed. More expensive seed will have much less of a weed problem. If you look on the label at the guaranteed analysis, you'll see Weed Seed and Other Crop numbers. Those should be zero or close to. Expensive seed will be zero. Hardware store seed will never be zero. This gets down to how much you want to spend. Is lawn care a hobby or a chore? If it is a chore, then go with the hardware store seed. If you want the nicest lawn on the block, then this is a hobby and you could justify spending more up front.

Other stuff
Aeration is generally not needed. It is very commonly done, but not needed. There are better ways to soften hard soil. Top dressing with soil or sand is NEVER needed unless you need to change your drainage. These materials can be a serious problem if you don't need them. Top dressing with compost is usually only needed if you have chemically poisoned your soil.

Organic fertilizer
I have been organic since 2002. It really works. Furthermore it seems to have solved other issues I was having with my lawn. The way it works is biological rather than chemical, so it is completely different. You can apply organics any day of the week, or every day of the week, rain or shine, summer or winter, and not have any problems. The only issue people seem to have is the "slow release" feature. It takes 3 full weeks to see the greening and improved density. My current favorite organic fertilizer is alfalfa pellets (rabbit chow) applied at a rate of 20 pounds per 1,000 square feet. You can find it in 50-pound bags at your local feed store (call first). I like them because rabbits are everywhere and they are fairly cheap this year. I scatter them by hand but the should go through a broadcast type spreader. If you can find alfalfa meal, that would be better and would go through a drop spreader.

-icides
Generally you should not need insecticide or herbicide. A few grubs are acceptable. When you get more than a dozen grubs per square feet, then you have a problem. Usually grubs are a late summer problem. June bugs or Japanese beetles swarm your porch lights in May, lay their eggs at that time, the eggs hatch and the damage begins. By late summer the accumulated damage finally becomes apparent. If you don't see swarms of beetles in late spring, then you likely won't have any issues. If you do, then wait a month and dig a few test holes looking for more than a dozen per square foot. Where you get into needing herbicide is when you put grass seed down in the spring and start watering 3x per day to germinate that seed. Summer weed seeds are germinating at the same time, but only when they get water 3x per day every day. If the soil dries out for days (or weeks) at a time, then you won't get those weeds. Of course Mother Nature has different ideas about when you get water.

Thank you VERY much for your response! I've been getting a lot of advice at home from my dad (who doesn't take care of his lawn) and a family friend (who hires people to take care of his lawn) so getting a direct response from someone with knowledge really is extremely helpful.

I can't say its a hobby yet, but it could definitely become one if we improve the quality of our lawn.

Thanks again.

Once it starts to look like one of the better lawns on the block, there is a tendency to make it a hobby.

Fix your watering and things will get better. Note that none of this is expensive. You needed to water, mow, and fertilize anyway. The only secret is in doing it right rather than wrong.

You need to decide now what you are going to do in 2 weeks. August is the beginning of your seeding window. If you want to kill the weeds or even the entire lawn, now is the time to plan for that. I just touched on seed selection and did not discuss preparation at all. If you want to reseed, please say something so you don't make any mistakes with that. It is really easy to do the right thing but a lot easier to do the wrong thing. We can save you time, money, and hassle.

If you have time, I would love to hear your advice for reseeding. As I said originally, I was considering renting a slit seeder, but I'd love to hear the right way to reseed, so I don't mess up!

August is the prefect time, because I'm a teacher, so I can take action right before I go back to school!

Thank you very much again for all your advice!

The two most common seeding mistakes are rototilling and burying the seed under topdressing.

Rototilling churns up the surface of the soil unevenly. When the fluffy surface soil settles back into a structure, it settles unevenly leaving a bumpy surface. Rototilling also destroys the existing soil capillary structure which allows for proper percolation of water and gas (air and carbon dioxide) conduction. The soil structure is established by the movement of roots, insects, and soil microbes over the years. When you rototill you lose all that and have to start over.

The second mistake is burying the seed. Grass seed germinates best when it is at a depth of between 0 and 1/8 inches deep. Seed on the surface germinates just fine in nature. If you are going to cover it with something, make it a very light dusting on the order of 1/2 cubic yard of topdressing per 1,000 square feet.

With that in mind, here's what I would do.

1. Kill off all the existing stuff
2. Mow it down as close as you can get
3. If you have a slit seeder, run tha through once with the cutters set at 1/8-inch deep. That will slice up a lot more fluff. Clean all the mowed grass and fluff away
4. Slit seed or scatter the seed
5. Roll the seed down with a rented water fillable roller
6. Water lightly 3x per day for 3 weeks. Water at breakfast, lunch, and dinner times.
7. When you have 80% germination start to back off on the frequency of watering and water for a little longer each time. If you start in August, the by mid October you should be watering a full inch of water about once every week or two.

I would use organic fertilizer but morpheuspa would suggest using a starter fertilizer. Hopefully he'll see this and give you a recommendation. He would also suggest covering the seed with peat moss. I believe either way will work. After you read his thoughts, you can decide. He really knows his grass.