on move 55 of your other line, 55...Qb6, 56. axb6 and white wins.
I loved this one

in the move list when you are talking about endgame wouldnt whenever you move Qb6+ be followed by axb6?
Well, some of his moves are good, if followed up correctly, so 47.g5 dosent deserve a ?? because instead of Fxg5 he could have played hxf5 and it was drawn.
It's a rare thing to say that you played a great game despite missing a quick knock out. The endgame here demonstrates that a two pawn advantage is not necesairly a win. Not the best game, but quite fun:
See the move list for possible variations.