This was a huge missed opportunity, in my opinion, but something tells me that you'll have more.
I agree. It is a missed opportunity because if you had turned him down then he would have really seen what it was like if you weren't there to pick up the pieces. He hasn't truly felt that yet. He doesn't know what it would be like to lose you because he knows he can come back without changing anything. He still has a choice and he knows that.
I just worry that he is using you. I mean he already doesn't want to take the classes? He should take them or he should be working full time...I believe you said he was only working part time.
Yes, technically it is his house but he hasn't been contributing at all, financially or otherwise. Maybe you should tell him that was a one night thing until he can prove to you that it is going to be different. Let him know HOW he can do that. Think about what YOU need.