I'd leave at 7:30 pm. You'll hit some traffic congestion here and there, but you'll probably arrive around 9 pm. Even if you had unusually bad traffic and were to get in at 9:30, that's still enough time for a 10:20 flight with checked bags. You'll have at least the priority line at T2 security (even better if you have Precheck).

If you use the domestic garage, it makes little difference. That garage is like a hub that is almost encircled by the domestic terminals. The D section for Terminal 2 (your AA flight) is right next to the E section (figures, doesn't it?). It's a very short walk to the D tunnel or bridge wherever you are in there. I recommend parking at the top (level 5) so you're right at the bridge level, or the bottom (level 1) so you're at the tunnel level. It's not a problem, though, to park in a middle level and take the stairs/elevator up or down.