Gosh... well... you have me there, I should not have drew. Perhaps I need to try and study end game.... because I don't think I would have thought of that... and the sad part is, your list of moves are perfectly logical too....
Where did I go awry?
In your drawn game 7... a6 was played to prevent Nb5. I think 10...o-o-o was a mistake for black. what I see is exf6 Nxf6, Nxe6 Bxe6, Rxd8+ Kxd8, Nxf6 gxf6 and white is pawn up. The most important thing you did wrong in your endgame is not to believe in yourself. Are you able to recognize when you're winning or not? Do you think you can secure a win? What is it that prevents you from believing that you can win a winning position? Something is obviously preventing you from asserting yourself to move boldly. Chess is one of those games that draws out your personality. If you're timid, if you don't like fighting, if you feel inadequate, you will not win. You had material up, trade down until you get the material advantage and push that advantage without fear or favor. I don't mean to sound too harsh, but if you're not willing to make those assertive moves, you'll never improve.
I really think you should start studying the endgame, but you could have won the game something like this: