CAMom, I'm really proud of you. You've gotten a good handle on your son. Don't be so sure he won't change though. If you interact differently with him now (not giving him all those perks and not giving in to him, even if he tries to guilt you out) he'll have to change his behavior towards you. He won't be able to quit his jobs if he needs the money, for example.
My daughter worked for Walmart from age sixteen up because we cut off her funds. We sat her down and told her that since she seemed to feel she could do what she wanted to do, then she would have to pay for her own "perks." We had to provide clothes so we offered to buy her a wide variety from garage sales and Good Will. Of course, she wanted nicer clothes so we shrugged and told her, "Get a job." Food? We provided three meals a day. Chips, junk food, McDonalds? "Get a job." For a while, she drove, but had to pay for her own insurance and gas. Maybe, in the long run this helped (we don't know for sure). Once she left home, and had to fend for herself (her choice--she had the choice of staying if she'd follow our rules and go to rehab), she decided she hated her life and wanted to change and she did. Motivation is a big deal with kids like this. They have to decide to change, we can't make them do it. But I'm positive that my daughter isn't the ONLY problem child who decided to change...lol. My daughter was WAY worse than your son. I need to keep feeding you nuggets of hope. Your son doesn't sound like an awful person or a bad kid. He seems to suffer from a bit of "I'm entitled" and some bad friends. My daughters peers were her biggest obstacle to getting straight. She had to move out of state in order to clean up her act (she moved to live with my straight arrow son who has a huge house, and very strict rules). The funny thing is, she looked up to her big brother so she followed HIS house rules where she disregarded ours, maybe because he's more of a peer. Look for possible relatives, in case your son needs to break away from his friends (just a suggestion). Talking to my daughter now (she has just turned 23), she tells me that several times she tried to get away from drugs, but her peers pressured her and she caved in. Peers can be powerful good or bad forces for young adults so living away from these losers really helped my daughter A LOT. At her age, we couldn't really totally stop her from associating with them while she lived with us. She would find a way. I'm rambling now...duhhhhhhh. I tend to do that...lol. I think you are on the right track. Have a good game plan for when he comes home. You're a great mom. He knows that too, even if he refuses to tell you that yet. One day HE WILL.