Not too sure about the setup with e3 and g3, the light squares can easily become weak if you're not careful.
Why not 12. Bxc6+ as the rook on a8 is hanging
13. cxd5 seems simpler, winning the pinned knight.
14. Bxc6 seems a positional blunder, if you were level in material this would be a really bad move, giving up your strong light squared bishop for a mere pawn. It opens up lines for blacks rooks and could leave the king in danger, luckily you were already up on material and so it wasn't too dangerous though.
16.b3 looks a little careless, king safety and development in situations like this! Slow and so something simple like 0-0 would have been safer and given less chances.
Not sure on the purpose of Qd7, if white is given an extra free move afterwards what is the queen going to ever do on d7?
Is the ending right because surely 41...Kxg7 and black may be able to hold?
here is a game i played last tuesday against an awkward weeker player with 25 q d7 a week move turned out be a postional sacrifice i don't expect any repies but here is the game anyhow enjoy it