16. Nd8 is a mistake. Black can now win your k night with 16. ... Ke7 since all the escape squares are covered. This is true for the next several moves as you both ignore it.
34. Nxc5? It's not necessary to give up your knight. 34. Rc1 would have taken care of the c-pawn without giving up the knight.
35. Kxa2 walks right into the fork 35. ... Rc2+. You need to make sure your pawns are defended.
37. Kc4 walks right into the fork 37. ... Rf4+. After that the game is a drawn position.

I recently played a 5 min game in which I drew even though I had an advantage. Where could I have improved? Thanks to all who help analyze.