I can't pretend I understand your position in this, but I actually can, I think, relate to your sons, when I was that age.
I had an extremely turbulent childhood, and honestly? At his age, I began to resent the world for it. I had a lot to mentally and emotionally deal with, that a lot of adults will just never understand how going through this as a child tears you up, turns you upside down and churns you before you've even had chance to learn coping skills. Many adults would struggle to have the coping skills, to be frank. So, cut him a break.
By that I don't mean allow unacceptable behaviour. I completely understand why you're feeling the way you are, you are on the receiving end of abuse, day after day. When you allow yourself to think and verbalise that you hate him - that's when I mean, cut the KID a break.
Secondly, be completely truthful with yourself about your behaviour. Do you lose it? Do you shout, do you scream, does your facial expressions let him see how you really feel about him? Really think about it and be honest with yourself. Does he look at you and see disdain, or contempt for him, during his outrages? Do you think he can sense you dread him coming home, your exasperation before anythings really started up?
Understandable for you, yes, but for him, he's a child, supposed to be unconditionally loved, and is clearly struggling, monumentally.
You have to be the one to lead by example. You have to keep calm, and you've already recognised your first major parenting failure - not adhering to boundaries. Of course he's going to keep at this for hours or days. You've taught him the exact point of it. More so, it's a shock to the system when you know people give in to you, and suddenly, it looks like they won't. There'll be panic, and an almighty fight against it. But like you said yourself, you're not doing it.
When parents see their teenage child struggling emotionally and mentally, they have an instinctual tendency to probe more, attempt to get more involved, have more conversations. That's natural - they're concerned. But often times, what teenagers going through something do need is a little space.
What I needed, and as a thirty-something adult, I will absolutely maintain, was space. Space from conversations. Space from demands. Space from expectations of how I should be handling it, or that I wasn't mentally handling it well. Space from being made to feel I was a disappointment, for something I didn't understand, or felt I couldn't even control, myself. I don't mean being allowed space to do whatever I wanted, and behave however I wanted. But I really needed understanding. I was angry. I didn't understand why I was so angry, and why it was eating me alive. I was pushed into therapy, and it made me resent those around me more. I really needed some space and peace to figure it out for myself without constant expectations and input. Many parents see their teens isolate themselves, or isolate from their parents during very difficult times, panic, and push and push harder. I didn't want to be taken out for meals, I didn't want to spend time with them at that time, I didn't want to be made to talk about it at therapy before I was ready. Honestly? I just wanted to be left the fuck alone to sort my head out and deal with it.
In no way am I saying allow him access to anything he wants, to behave however he wants. I'm simply offering the other side from someone who remembered it well. I wanted peace, to myself, and just left be for a little while.