Fall is the ideal time to re-seed/overseed, but in my opinion they should have overseeded in early spring. The #1 way to prevent weeds is to have thick, healthy turf grass, mowed at 3.5-4 inches. A healthy lawn will block the crabgrass from getting any sun and ultimately smother it. Granted, you still would have had plenty of weeds this summer, it's not like your first overseed in the spring would have magically created a lush lawn, but it would have given you a foundation, so that this fall you could really overseed and by next spring have a thick, healthy lawn.

It seems like a waste to put grub control, fertilizer, and per-emergent on sparse lawn. Really, they were just fertilizing the weeds. Timing is very critical on the pre-emergent, especially so with organic corn meal gluten. You need to put it down when the forsythia starts to bloom or the first 3 consecutive 50+ degree days. If they missed that window, it's effectiveness is compromised. Depends when in April they put it down. Should have been down the first week, the latest.

If you have that many weeds it would be best to start over completely. You need to really kill all those weed seeds and the only way to do that is to either use roundup all over the lawn or preferable without using chemicals by using a process called Solarization (see link below). You could get started doing all of this right away and be ready by late august for core aeration, overseeding, and most likley lime application, but I would HIGHLY recommend having a soil test done. UConn may have an extension office, I know Umass does and it is cheap and provides PH and all the other key nutrient levels of your lawn.

Good Luck
Shawn

Here is a link that might be useful: Lawn Solarization