Okay so you tilled in lots of compost and you still have hard soil. Hmmm. I'm the lone wolf who says that compost is overrated. You're helping to prove my point.

Shampoo is not a trick. You can buy the same thing for $70 per gallon at specialty nurseries. It was carefully tested and found to work very well. Then it was chemically dissected and determined to be very closely chemically related to shampoo. Why wait for it to cool down?

How often are you watering and for how long? Watering improperly might have been part of your problem in the first place. My mother (in Temecula) watered her Marathon very poorly and my niece (in Hemet) still does. Grass can be very temperamental when you don't water it right. My sister in Riverside doesn't water and has wild bermuda to show for it.

Dead Marathon has to be resodded or seeded. Now is a terrible time to seed, so sod is by far the best choice. Fescues like Marathon do not spread like bermuda does. If you resod, do not rototill. That was a mistake the first time. Don't make it again.

I will definitely check the watering soon, but it has been over 95 in the last few days which is very unusual for this time of year.

I went to the store today and will do the shampoo treatment in the morning. As for patching in the grass, I will continue to try to eradicate the weeds through the summer and will seed in the fall (budget consideration).

Also keep an eye on quality of soil, so use different methods using which we can improve the quality of lawn soil like using Fertilizers, pH test, organic fertilizers etc. However most methods will require time, different treatment. As you said that by considering the budget, so soils only need little improvement to create stronger and good quality Turf and which will definitely reduce the your maintenance.

Here is a link that might be useful: Lawn