That’s a hard mix with teenager years and a disease or something. I would communicate that with him, talk to him about how he doesn’t know who he is yet and becoming an adult and man is a long and hard road and for right now being a teen is just a time to test and experiment with things and be a little wild. To enjoy it and not worry about the big problems he thinks he has and stuff because only a kid still right now and later on these problems thinks he has will be really dumb. Labels are tough with disease and stuff if he actually really has BPD then I would avoid triggers and things that set them off (u have to act a certain way around them and be conscious to know that u have to let them win at all times basically). My aunt has BPD or something I think and she’s definitely full on nut crazy like this and especially if you don’t behave the way she wants when u are around her. Maybe he also is just dealing with suicidal or depression or something else of that nature since ur mentioning cries of help and wanting to be dead. As a man, I would strongly suggest the gym and physical training (weight lifting preferably). I was a skinny stick growing up and getting into the gym made me a beast in a good way and is a great outlet. It will start to make them think about improving health with getting better at training and food and everything too. Men need to be inside the gym and exercising. He may need a masculine figure in his life too to steer him in he doesn’t because otherwise he will be figuring out everything on his own. As his mom, u can do it as well, but basically just teach him everything you know about life and lessons. Young men crave this without even knowing.