Hey Heidi, so sorry to hear what you are going through.
I have a 23 yr old son with BPD and narcism and three other kids.
In the end what helped me deal with my son was getting counseling for myself and being told repeatedly that a) I had to save myself and not get caught up in the FOG -Fear, Obligation and Guilt that my son's threats to walk out or kill himself when he didn't get his own way. I had to learn I couldn't change him but that I had to save those who were in most need first-my marriage, my husband and then my other kids who were becoming seriously traumatized by my son's actions.
Once I got that into my head I also realized that I had to stop letting my son drag me into his world of rage and emotions and threats because if I jumped in there with him? Who would be there to save him one day if he finally worked out he needed help? No one.
So I put up clear boundaries for myself-really basic things like him not screaming and shouting in my house and treating us with respect. It took a long while-and he got worse when we changed the game on him. I learned to use the SET techniques on him and not get involved in rows, arguments or his distorted thinking. It wasn't easy. I thought my heart would rip in two but I did it because I realized I couldn't save him and that by enabling him and giving him everything out of fear I was just making him worse.
Baby steps. Get help for yourself. Start establishing boundaries and stick to them. Let him fail, let him walk away. It's the hardest thing I ever had to do in my life because I'm his mother. right? But you know what? It's almost 3 years since he stormed out in a rage and he's got a job, he's off his addiction to pain meds, he's functioning. He did all that because we were no longer prepared to do it for him. But he did it.
You can't save your son, that's the truth. What you can do is let him deal with his own issues and stop blaming everyone else and expecting them to jump.
FOG and SET are explained in more detail on the side bar on the right.
It's hard but its worth it to get your life back-especially for your other kids.