Got stupid lucky with last second mate
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Black's undoing was your pawn structure on the queenside and the fact that you used your bishops effectively. You missed several chances to deal even greater chances, but overall you played well.
2. I would have preferred exd5. It would have led to a faster game with a lot of opportunities for you.
10. Bxf6 would have led to a strong attack on the king-side. Consider this: 10.Bxf6. Here if black decided to save the queen with 10...Qd8, it would have led to a very dangerous situation. 11.Qh5+ g6 12.Bxg6+ hxg6 13.Qxh8 and black also loses his g8 knight too. If he plays (13...Nf6 then 14.exf6). If he prefers (13...Nh6 then 14.Bxh6 ... notice your dark bishop sitting at c1. Black can't take back with 14...Bxh6 because his dark bishop is pinned due to queen at h8).
However if he played 10...e6, then you would have his f-pawn for free.
18. How about Be3 instead? It is a bad move but at his level, it would have worked. It is a trap for checkmate which CAN be countered (and you would end up hurt) but it would do at your level.
10. Yes, I missed the 2x attack on that pawn with my B and Q. I insta-knee-jerked the en passant for some reason. I didn't even look around. Maybe to open center knowing I was castling soon.
What was the Be3 checkmate trap?
18.Be3 Nxd3 19.Bb6 Nf4 20.Qa1#
After 19.Bb6, black can save his game only with 19... Bd6 so that 20.Qa8 can be countered with Bb8
Ok, I see the trap now. Thanks for the analysis!