That missed defense by Ivanchuk where the blocked h-pawns allow that normally lost Q vs knight's pawn ending to be drawn is cool! Very nice game with many critical moments, and congrats on the win
I think that 4.cxd5 is the right move against 3...h6. Then white follows up with Bf4, e3, Bd3, Nge2. Compared to Karlsbad with Nge2, white has won a tempo, because in the Karlsbad h6 usually attacks the Bg5 which then goes to f4. Especially when the black squared bishops get exchanged I don't see a definite way to 0.0, White just has the better bishop.
Here is a recent game by Donchenko:
I just see, you had this on board in the same championship, two rounds later against Erdogmus, and the game went 9...b6 10.O.O c5! 11.Rc1 Ba6! which seems to fully equalize. Interesting is 10.Nf4!?.
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