You know, when I was on state aid when my oldest was first born (she is now almost 16), I was working, and I was also going to school. I was not with daughter's Dad. He was a full time college student, and still, the courts ordered him to pay towards support. I got $48 per month. Now, obviously not even enough to pay for diapers, but you know what my point is? HE PAID IT.
Your guy paid nothing unless it was taken out of a bank account or out of tax refund. NOTHING. Zip, nada. He just decided, on his own, it was too much to pay. So he paid NOTHING. The state, and the taxpayers of that state, supported his child.
I get it...he couldn't afford that much. But he is in this position not because your state is a big ol' mean state, but because he did NOTHING. He didn't try proper channels to protest the amount, he ignored it. He made ZERO effort to support his own child. The only reason that doesn't matter to you now is he "luvs you and you are a family!"
Guess what? I don't even like my ex. And I still recognize that he TRIED. Your ex did zilch, he is in a bed of his own making, and dragging you down with him. No money for rent? HIS FAULT. ONLY HIS. He could have made an effort, but even now, it isn't him on here trying to get info, it is you. See a pattern of him doing nothing? First he lets you figure out how to support your joint child, now he is letting you figure out how to clean up the mess.