Nice game.

Move 6: "I dont know a lot of theory here, perhaps Bg5 was better".

Your move seems good. Bg5 would encourage eventual exchanges (after Be7), which isn't what you want there.

"And not cxd4 which creates an unecessary isolated pawn"

Except that in those kinds of positions an IQP can be considered a strength, as well as a weakness. In fact, accepting it is probably the only serious try for an advantage. I can't criticise your choice though.

In your variation to move 20, 22.Bxh7+ leads to mate: 22...Kh8 23.Bg6+ Kg8 24.Qh7+ Kf8 25.Qxf7 mate. I only mention it because it's an important motive to know.

23.Rd4 seems better. Bringing your last piece into the attack.

34.Bb3 just wins a Knight.