My ex-fiance pays child support only sporadically, and what I do is just budget as if I'm not going to get anything. I don't know if that is an option in your situation, but it doesn't sound like he is going to be cooperative any time soon. Is there any way to decrease your expenses, maybe dropping or decreasing extracurricular activities? Using family for babysitting and decreasing the time with the babysitter? It sounds like you and your lawyer are doing all you can and you'll have to wait for him to get the idea that the judge is serious about him needing to pay CS.
On the plus side, if he does get his act together, he will still owe the money, even if a long time has passed, so just like your lawyer said, it's not lost.