While I wouldn't necessarily "divorce" my SS, it would be healthiest IMO if he was cut off from ALL financial assistance (phone, car, old school bills, health care, everything) if he's choosing an independent path. That doesnt mean no friendly chats and visits, it just means he wants to be independent from you (though all you adults know it won't help him in the long run)-- so let him feel what full independence feels like.
You're the Smom though, so unfortunately you probably won't be listened to even if you are the only one making solid objective decisions. Whenever you feel anxious about him, pray and remember all the good things about you're relationship with him. Eventually he's going to grow up a bit and he's going to need encouragement and friendliness, not distance and resentment. Good luck!