No advice but I'll be a pocket rider if you wish. One of the hardest things my mother and I did was to tell my daughter that we would not bail her out. She is bipolar and back then she was untreated and drinking and using drugs. We did help her get a lawyer to go though the mental health court where a condition of not going to jail was to accept treatment. At the time it was very hard and she hated us but now she says it was the best thing we could have done for her. She's 34 and has two kids and has had a relationship with one man for 10 yrs.
Your son may very well fight you and say he hates you but you are doing what you think is in his best interest so hold on to that thought.