Dixie,
When I mentioned "just weed", I wasn't slamming you at all. I apologize if it came off that way. It's the mentality of our difficult child's I was referring to. "Just weed" is their excuse and explanation that they don't think they are doing anything wrong.
I thought he was under 18 when you mentioned a high school diploma, so you're right - being 18 means he is responsible for himself, such as it is. As Nancy said, at some point you will have to draw your line in the sand. Only you can decide how much and what you will deal with. The out of control mood swings and spouting off at you are all typical of drug use. Hugs. It's so hard to have a battlezone in your home. I've been there done that.
As I mentioned, for our son, he realized he was out of options because he was arrested. He was already in the residential facility by the time his court date got here, and although the prosecutor wanted to remove him from the Residential Treatment Center (RTC) and put him in adult jail, thankfully the judge disagreed. She felt that he was at least in a voluntary program, which was secure (locked), and she mandated that he not be released from there until the staff, counselors and doctors felt he was ready. It took 10 months.
My son's treatment program was a dual-diagnostic (psychiatric and substance abuse) and was locked, although he was there voluntarily. He had to reach different plateaus before being given rewards such as visiting home, even getting a job at a sub shop nearby. It was a wonderful program (unlike the first one we put him in when he was 14). My son never did go back to the drugging, but in later years, turned to alcohol, which is still substance abuse - just a different drug.
For us, we refused to have him in our home when he was drugging. As I said, we gave him his options - he could go to jail or enter treatment, but his scenario was different than your son (at least presently), as our son had been arrested.
Please know that in this corner of cd.com, we understand. No one is questioning you or what you're going through. Everyone has different circumstances and our difficult child's each react differently to different plans of action. I can only tell you what worked and didn't work for us, but it sure wasn't an easy road. We called the police on our son several times toward the end of the drugging, as he was stealing from us and stole our car on a few occasions and our goal at that point was to keep him alive - even if it meant him going to jail. It was such a dark time in our lives and one I could never re-live.
Hugs to you. I know how difficult this is.
Deb