Hi Baddog,
I'm so sorry for what you are dealing with. I'm glad you found us here.
I would sign the car over to him asap. As long as it's in your name you are liable for anything associated with that car.
Well good, he has a place to go. He will find out soon enough that sleeping on someones couch for an extended period of time without paying any kind of rent is a quick way to end a friendship and also get booted out.
It's no different that him freeloading off of you.
Too bad he won't go find a job in sales. It's good he know how to make some money online selling stuff but it's not okay to steal from you and your wife.
It's not easy but you may get to the point with his stealing from you that you may contact the police to press charges. I had to do this on more than one occasion with my son when he was still living under our roof.
The good thing is your son is still young enough to turn things around, of course that's entirely up to him.
What I can tell you is you and your wife need to have very strong and firm boundaries in place. What you will and will not tolerate. Have a consequence in place and make sure to follow through. Be very careful as the line between helping and enabling is easily crossed and becomes blurry.
Helping isn't helping when it's enabling.
Please don't look think of it as "kicking" your son out, you are liberating him to live his life. From what you have shared, he sounds like he feels he's entitled. Taking money out of his mothers purse and thinking that is okay is an entitled attitude.
Keep posting and let us know how things are going.