mar37, your son is not just smoking pot...he's doing some serious drugs that make him a danger to you and others. Choking you is very serious. I know you want to think it's just pot, but it isn't and his friends are proof that he is into drugs. Druggies hang with druggies. I had a daughter who d id drugs and we thought it was pot only too, but after she quit we found out it was speed, meth, cocaine, ecstasy, you name it. Please be careful. Your son is in dangerous territory.
My thoughts: If you can, put him into a hospital. However, I do not believe this is only a mental health or behavioral problem. If you have younger kids or value your own life, I would not allow him to live at home anymore. Let Dad keep him or look into residential or foster care after hospitalization. If it turns out to be strong drugs, and I think it is probably a form of speed or even the dangerous synthetic pot, he needs rehab. I mean, I could be wrong, but I would be extremely surprised if I am. Drugs is what usually make our kids that violent. It doesn't help that there is mental health issues in his family tree, but it is a fallacy that the mentally ill are often violent. They are usually not violent just because they are mentally ill. But drugs and mental illness do cause violence. Remember...
Your son is 50% his father's DNA whether your son saw him or not and nature trumps nurture every time. Well, maybe not EVERY time, but very often. His DNA is a part of him. Even pot can deeply harm somebody with those latent mentally ill genes in him. Do what you can before he is eighteen, but don't let him live with you again. That's my two cents from experience with daughter who took drugs.
The police sent him to Dad to avoid sending him to juvie or a mental hospital AND because he is a danger to you and they are concerned. Maybe you can get him admitted to a hospital where he can be drug tested. However synthetic pot, which is VERY dangerous, does not show up on drug tests. Many drugs don't show up and the kids know which ones don't. I'm so sorry for what happened.
Hugs for your hurting mommy heart.