I'm sorry I haven't responded before. It is so exhausting trying to manage their lives for them isn't it? I remember when I was 20 and commuting to college every day while working full time. I had a checkbook and took care of my bills and didn't ask or expect my parents to figure anything out for me. I don't know what went wrong with our kids who have no sense of financial responsibility.
If and when your son comes back make sure you have your boundaries set and that he knows what they are. He is old enough to get a job and be responsible, it's up to him. But oh do I understand how hard it is to detach.