There is so much I regret not doing, and I also have tried my hardest to help him.
That's just the thing- CC or I didn't do anything but stand by our boundaries. We couldn't fix the kids, we couldn't change anything. Only the kids could do that by their own actions. And until they're in a place where therapy and getting better is easier than everyday life, they won't take that step.
Every time your son screams at you, he becomes a little more entitled, a little more arrogant. Why? If he screamed at a friend like that, they'd probably hit him and never speak to him again. He knows that. Yet with you, you're taking the abuse and feeling shameful...that tells his sick mind that he's justified in the abuse, that you actually deserve it.
He's the victim in his mind, not you. He deserves so much more and you never do enough for him.
I've said this so many times, that's the mental illness talking. You can't have reasonable conversations with him when he's in that mindset. You have to walk away or make him leave because his emotions have taken over in that moment. Then you can follow up and try to have a conversation when he's more level-headed.
I'll repeat one other thing- my daughter said she hated me consistently, called me the worst things you can call someone. Yet every time she was in trouble, she called me. Why? Because her words meant nothing when she was disordered, she was just venting and having a temper tantrum. And she never apologized because she was too ashamed. Again, that's the mental illness aspect of this.
It's all emotional explosions like a volcano...they erupt and then they balance out for a bit.
I'll say one more thing; currently you and your husband suffer from mental illness. Not like your son, mind you, because his is permanent. Yours is due to extreme stress and anxiety, it leads to depression and many other illnesses both physical and mental. It also takes a severe toll on your body. For example, my hair was mostly grey in my 30's. I had a heart attack in my early 50's. All from stress and worry over my kid.
You can continue to struggle, you can continue to fight a battle that you can't win, or you can set clear boundaries. I'm telling you, it was the best decision of my life and once I was out of that situation for a few weeks, everything about me began to change. I slept better, I regained my focus, and I found inner peace for the first time in a decade. I was horribly depressed and had no idea because that was life, that was my normal.
What I'm saying here is that you are no longer responsible and you need to heal. Nothing about this is a "you-thing". It's a mental illness thing and only your son can decide to take active steps to get better. Even forcing him into therapy doesn't make a lot of sense because he has to want to change. Until then, the best physicians in the world can't help him. He has to want to help himself and you have to help yourself as well.