Quote: If he is disabled then its critical that he go back to court to get the orders modified based on the fact that he is disabled. That is where you need to help him.
Amen. So he has not yet been approved for disability? Has he got an attorney to assist him with filing for SS disability? He isn't sounding totally unemployable in the future to me. It's not at all certain that SS Disability will think so either. I think it is unhelpful to blame the whole situation on the ex wife. He's also one of the parents of the child (ren) No one who is not one of the parties, is looking from the outside could really say with decisiveness that he's a blameless lilly and it's all her fault, she caused the whole thing.
But if as he says, he is "not going to fight it" and is just letting it play out, why, if you aren't going to help hire him an attorney and encourage him to help get these things settled, you're not helping. This suit sounds like her attorney advising her to get this support situation established, not an effort to kick him while he's down. (Regardless of who she's with, married to, being with, made up with, she still has your son's child or children, is due the child support, or the state for any aid she has received will pursue the child support.)