Couple of questions inline....

I'm not much higher rated than you, but I could try to offer some advice I guess. What were the time settings for this game?

6......a6 I think is a slight blunder, bg7 would have been better as it opens up his diagonal on your slightly weakened dark squares and your bishop wasn't really doing anythink threatening.

11.... a5 I think is a blunder as well making your knight a bit of a monster on the b5 square. You played well there with 12.Ncb5

14 Nc6 another good move, your two knights are now very strong, him failing to notice this basically wins you the game

15. b3? I think Bd4 is your best move here.

21... QF5 is absolute suicide and makes your decision to not move Nxa5 on the move before very smart.

1- grabbing space with pawn pushes can be good or disasterous depending on a few variables in this instance i would not advise it as black could have responded a lot better and traded for an open advantage.

2-if you mean moving the c2 pawn instead of a2 in defense of the knight then i would say yes as that move frees up the pin of your queen if you had to move the knight.

3- actually the trade was technically equal because a rook and a pawn = 6 points which you traded for a knight and a bishop(each 3 points) eaqualing 6 points

4- yes

5-BOOM goes the Dyanmite.

Why is that a good move?  B/c my bishop is more central?

Wow, I didn't even notice I could have taken the rook with Nxa5