I'm so sorry to hear about your situation. I been there before and when the man loses his job, leave the house, they believe that they can just ignore the life they created. They should still be providing at least something. Do whatever you can to get whatever assistance from the Government/State. It's there and available don't sell yourself short. take care of you and your son first.
Who left the home? If the relationship was ending due to reconcilable difference and you both agreed to it, then share the cost of the divorce, if not...allow him to pay for it, he wanted out.
Think about it, no matter what your husband does, he is definitely taking care of him...Didn't you just say that he will be graduating soon. Have you thought about doing the same thing and not relying on this man.
I know it's hard but you have to stand tall, take care of you and make sure he pays your parents back. Was there a signed agreement, if so, this could help in your parents favor, if not, he can claim it was a gift.
I think it's time that you sit down and talk to a good lawyer for your sake, so you will be taken care of if and only if your husband receive a a lump sum of dough. Don't share with him your decision, just do it. In the end, you will understand. Dear, your husband is going to take care of himself first.
GET A GOOD LAWYER
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