

right. i just went through the entire game, and black was definitely leading, until move 35. I'm inclined to place 35...Rg6 as the losing move, as there was the simple reply 35...g5, leading to an easy win. this is, of course, ignoring all the other mistakes before that.
I like Bxf2+ first because if he takes Qb6+ saves the Rook and if he doesn't it's still the same thing as Qb6 first. Just a matter of personal preference.
I lack a suggestion to your main question. Game is so vulnerable on both sides. I can easily see myself castling as well. I might have tried (in your line)
10 Bxf2+ KxBf2
11 Qc5+ K whereever
12 QxBc4 and regardless of his response, you have good queen taking and possibly king's rook taking possibilities.
Even on move 40 I think you had good drawing chances. 40 .... Kg5 is a conceptual error, you are never going to shepherd that pawn to promotion. Alternatively, leave the pawn on g7 (The White King must waste much time to pick it up) and instead play 40 .... Ke5, when you pick up some of the loose White pawns. The ending I propose is unclear (to me anyway), but better than the obviously lost one that you chose. I hope this helps a little.