avoice, it may sound harsh to you but i feel jail time for him might at least make him think where he's headed in life if he doesn't change. it sounds like thus far he's gotten away from punishment. these behaviors usually escalate to more serious behaviors. but as you said only he can change himself. as a mother too i know how very upsetting all this is to you. we always want the best for our kids.
k2 use can be deadly. i'm surprised he has not experienced a near fatal event. but his use of this you cannot control either. here's some info for you the best suggestion i can offer is speak with him about your concerns. encourage him to consider a drug re-hab. but please know the decision falls into his lap. i wish i could be of more help.