I don't like 7...Qxd6 at all : you've given a pawn for some development advantage - you shouldn't trade your strongest attacker !
You played very well afterhis f5? and the attack starting with Bb4+ is really nice 
In the opening, I wonder if f6, instead of d6 is playable ?
I'm not a big fan of 4.f4 because I like to keep my center closed longer. A big center does require a big army to hold it. The Queen swap was not good for either side in general. It is the most mobile piece and when there's a lot of air around the king she's best kept on the board. (In your case it was ok to do so).
A lot of moves for both sides were not examined. Take a look at earlier castling options for White and also 11.Bf4. This should give you and idea of the scope of play.
Can you help me with analysing this game: