I think your son has issues he needs to resolve now. I would not be concerned at all about grad school. Where is he living? If he is at your house, you can help him set some guidelines while living there.
- He needs to get counseling ADAP to figure out what went wrong...and how to get on some track for,the future. And realize....this might NOT be the same track he was on.
- If he is living with you, a condition of free rent could be sharing the information with you. In addition, he can sign a FERPA release at his college which can give you access to his information there.
- If he doesn't want to share, is it possible there is something that is stills that he is hiding from you?
Please, get him the help he needs to resolve whatever is going on. The future will sort itself out when the time comes.