@ladee I know that you probably already understand what your son is doing, but I will remind you, so that you won't forget. He's manipulating you and trying to guilt you into whatever it is that he "thinks" he needs, wants, or believes to be his truth and wants you to see it. I doubt that he will do himself in or even try. It's a ploy, usually seen by teenagers that haven't fully developed their brains yet.
Your son is an adult, he makes his own choices, be it good or bad, there is NOTHING that you can say or do at this time(or possibly ever) that would make a difference. Everyone perceives THEIR own reality, memories, life, it's THEIR truth, just as we have ours.
My daughter has such a skewed reality of her childhood that I sometimes think, "Where the f*ck did she come from and just where did she get these things from?" She once told me that I withheld medical treatment from her and she almost died. Ok, she woke up one morning, she was 15 at the time. She complained of a real bad stomach ache. Told her I thought it was her appendix and we needed to go to the hospital as soon as possible, because she had a rare bleeding disorder. Her reply, "f*ck that, I'm not having a scar on my body, there is no way, Becaus Pat (her BF at the time) just had his out, and he has a nasty f*cking scar. They are not doing that to me." We argued, we fought, and then I just said, "Well, Deb, when the pain gets bad enough, let me know and I will take you to the hospital" I never left her side all day long. Finally at 8pm, she couldn't stand the pain and we went to the hospital. YES! I knew it was dangerous, but I also knew that fighting her was a losing battle. So to this day, she tells people that I withheld medical treatment. It's HER persecution, and nothing I could do or say can change that. It's her truth, just as your son has his truth.
Even if, god forbid, that your son should follow through with his threats...... KNOW that there is nothing that you could have done to stop it. When I attempted, no one on this earth could have said anything to make me change my mind.....
I'm sorry that you are going through this, and I wish that your son could just grow up, become the adult that he is supposed to be, and learn to talk, instead of unsung the manipulative things he does. I hope that you can one day come to terms with all of this, and know that..... WE DID THE BEST THAT WE COULD!!!!!!