We moved in 3 years ago, a new build. We sodded our 1/2 acre lot in 419 tifway. I've been mowing frequently, and fertilizing with a high nitrogen fertilizer every 4-6 weeks, and trying to get an inch of water on it a week. However, we did build on a pasture...and pasture surrounds us on all sides (2 sides they are directly next to us). So I know that I'm going to have problems.

Right now, crabgrass, is really starting to take over my back lawn. I'm in Northeast Texas, and today is the first day we've had high temps under 85. I do have some weed killer with crabgrass control bought at the big box stores, but it says it could kill my bermuda if applied when daytime temps are too high. We are staying below 85 for the next 4-5 days, then it goes closer to 90 in the middle of the week.

My questions are:

1) Should I forget about applying a post-emergent herbicide this late in the season? I did put on a pre-emergent this spring, but I didn't pay too close attention if it had any crabgrass control in it. Not smart by me.
2) If I do spray a crabgrass control now, when do I need to apply a pre-emergent fall application? Or do I at all?

I'm really clueless here and would appreciate any help. I have attached closeups of the biggest infestation areas (not long after mowing), as well as showing whats just over my back fence. FYI, these pictures were taken a few weeks ago.