Ok, I understand your point of view better now. Sounds like you could send him a demand letter for what he has not paid that he should have (provided you kept records) and then take him to court for a judgement if you wanted.
I wouldn't worry about him filing or custody. Even if he did you could probobly move for a summary judgement, have it dismissed and ask for attornies fees.
I don't agree with move aways when at all possible whether it be the custodial or non custodial parent. Since he is the one that moved away, I personally have very little sympathy for his situation.
