Nh5 wasn't a very bright move. Your knight at a3 is poorly placed, you should help him, as he won't help if you don't. I would have tried c4.
Right after b4, You should have tried Nd5 and exchange the knight for a bishop. It was surly the last move.
Rd7.
Maybe Rf3, with in mind that the king will safe on e2 or farther away.