Second Annotated Game

This is my second annotated game. This is a live game on chess.com 30 0 against a stranger. There were two moves that were very difficult for me.

The first is 16.b4. I felt I had several good options. I was probably too cautious in my final decision of advancing a pawn when I could have won material.

The second is 20.Qxh8 which wins a rook! Here I was concerned that I would not be able to safely extract my Queen from the corner. 

At move 44 White has a decisive advantage and Black resigns by abandoning the game. Although I am happy to win I do not like when players abondon games. 

What do you think?