Thank you for you input!
Yes, 12...Nxe3 felt rather simplistic. I suppose both of the alternatives give in my sketchy notes are stronger. Qc7 is a trade mark of The Lion and a5 might very well create som added tension along tha a-file.
13... Bg5?! is clearly worse than I thought last night after the game. There are several better moves for me (black) and a few ways for white to penalize my oversight.
True, he did blunder but there are of course still a lot of "play" in the position and more blunders to come from the two of us. Still, a win is a win.

Some quick thoughts:
11...Ng4! 12.Rad1 Nxe3?
Why immediately capture? Your knight is not threatened and White's bishop had no good squares to flee to. Often, maintaining tension is better.
13.Qxe3 Bg5? 14.Nxg5 Qxg5 15.f4?
Your opponent missed a chance to damage your pawn structure. After 15.Qxg5, I think combined with the open d-file, they have the better chances.
16.Qxf4 Qxf4 17.Rxf4 Ne5 18.Bxf7?? 19.Nxf7
Blunder. Your opponent apparently missed your knight on e5. There's something to be said for tactical sharpness, which you had a leg up on. :)