I second the suggestion for mediation. I just had a mediation for a modification of a prior agreement done for $90.
If he's belligerent and refuses to cooperate in mediation, you can ask the mediator to write a letter of recommendation describing the terms under which you mediated and whether you were both, or neither of you were, cooperative. The judge will usually take into account the fact that you tried to mediate first and one of you was game and the other was wasting time.