So it looks like I can finally take advantage of the fact that his Queen and rook are sharing a diagonal.

12...Nd5, unless I'm missing something, doesn't lose a piece because 13. cxd5 is met with 13...Bf6 and after 14. dxe6 Bxe5 15. exd7 Bxa1 I'll be up an exchange as there is no immediate way to protect the d7 pawn.

I'm expecting IANAWW to answer with 13. Bb2 but given the way he's played the game he may very well go for the exchanges.

Actually it looks like 13. Bb2 drops the bishop. I'm not exactly sure what whites ideal reply is here. Looks like he'll have to retreat his queen with something like 13. Qg3.

I can then follow with 13...Nb4 and if 14. a3 then I play 14...Nc6 with the intention of eventually placing it on d4

Looks like I am going to lose a pawn

a) 29. Rxc4? Rxc4 and Black wins because of the fork on d2.
b) 29. Bxc4 Rxc4 and now
b1) 30. Rxc4? Nd2+ and Black wins
b2) 30. Nxe4 Rxd4 31. Nf6+ Kf7 32. Nxe8 Rxd5. I think the Knight is trapped.
c) 29. Nxe4 Rxe4 30. Red1 (30. Rxe4 fxe4 31. Rd1 Rc5 and I think Black wins the Pawn on d5) ...c3. Now,
c1) 31. Rxe4 c2 and, again, the pawn in d5 seems lost.
c2) 31. bxc3 Rc3. My Bishop sucks, but my Rook is active. I should be fine there.
d) 29. Red1. This seems to be the worst-case scenario, and I think gambit will find it. I plan to play 29. ...Nxc3 30. bxc3 Rc5.
d1) Now 31. Bxc4 is met by 31. ...Rec8. But he will obv play
d2) 31. Rxc4. Welp. Now 31. ...Rxd5 32. Rxd5 Bxd5 33. Rd4 drops a Pawn. Hence, 31. ...Rec8 seems my best bet. Yes, I still lose a pawn, and he has the very annoying 32. R1d4, but at least his queenside pawns are weak. Besides, I don't have a choice.

He's done well to weather this raid down the flank and its cost me some material too. Running out of things to do, attack has broken down. Need to think.

I believe the only reply here is 14.Qg3 to which I plan to reply 14...Nxc3 15. dxc3 Rd8 (haven't decided which rook yet).

Currently trying to analyze lines that instead involve 14...Nb4 to see if have more to play for.