Hummm, shutting off the wifi should get his attention. Now make deals with him on how to get it back on. Start easy. See if there is any place that he can volunteer at for just several hours a day.
Frank, I don't have any real solutions for you, but want to say you are very kind and generous to have taken this difficult young man in and given him a home. Prayers somehow he turns a corner and is able to live a more positive life.
Ahh. I feel for you and the boy both. This is really hard. So, was he ever evaluated for any delays or issues as a child born to meth addicted parents? Does he have developmental delays? Learning disabilities? What's going on with those? What kind of mental health treatment is he in or has he been in? I know it is hard as once they are 18, they can refuse care. But wonder what would be motivating for him. Have you considered anything like trade school for him? That kind of gives him a future of independence.
I don't think I could just throw him out either. Boy has had a traumatic life full of sadness. I am so thankful you took him in and have provided for him. But it's still emotionally hard for someone without mental health issues and since he does, it's that much more complicated.
How does he respond to house rules?
Crisis hot lines are for suicidal people. This is a chronic mental health problem, and for that you need someone who treats that to treat him, which would be a psychologist to start with and a psychiatrist if medication is determined to be necessary. Does he have a job? Does he go to school? If not, you need to give him an ultimatum that he has to go to school or get a job, and given that he's now 18 and I'm assuming from what you say considered legally an adult where you live, it's up to you if you want to keep him as your dependent or not. I doubt you can get him declared incompetent if he's capable of understanding what's going on. At some point he is going to have to leave the nest, and if he's not willing to work or go to school he's not a child or a boy, he's a man, and he either starts to act like one or you are going to eventually going to have to part ways with him. He needs to know that and then make his choice. You can't force someone to conform to your wishes if he's an adult, but you can force someone to live by your rules if he wants to live under your roof. It sounds like he is profoundly troubled, and troubled people have a very difficult time coping. That's why he needs professional help, and the only thing you can do is force him to choose that or finding his own way in life. One thing to be concerned about is whether he shows any tendency to be violent or act in criminal ways with others the way he is stealing from you. Jail won't help him any.