I hope you don't mind that I am not a 2000 rating.

1.) Well you did a good job with your opening, playing the ruy lopez. The opening ended when you played 5. Nxe5, which was a weak move, and black wasn't skilled enough to take advantage of that move. Better would have been c3.

2.) The game was pretty much over at 8... Nf6 9. f4

3.) 21. Rg3 was your only other weak move, but you were so far ahead that it didn't really matter. 21. Nc3 would have been better.