J.C.
Whoever is the custodial parent is the one who has the right to claim her. I know this for a fact because my friend just went through this. If I were you, I would tell him that you are going to claim her because you're the custodial parent. It will probably not show up until next year if he does go ahead and claim her. You will receive a notice stating that two different social securities numbers claimed her social security number. It will say that if you are the custodial parent, to disregard the letter. Her father will be required to pay back all of that money from the previous year. You won't have to worry about anything or deal with anything.
As far as who to file with, I would say that if noone has any ideas for someone, to call H&R Block and a few other places and figure out which one is cheaper.