Like I said in my previous post, he knows now what he is losing.
He took advantage of you so long and now that this power of his is gone, he is lashing out at everyone: you, him, the world, etc.
He won't die, although he says he will. It's a common reaction that people have when they lose something as valuable as a loving partner. The role he played in the relationship up until this point was to hurt you, keep you down, oppress & suppress you, make you feel that his treatment was good enough for you. You've wised up and see that you deserve better, you've told him so, and you told him in a way that he actually believed you this time - that was the difference and that's why he reacted the way he did. I'm sure before all of this he knew that you weren't comfortable with his "polyamorous" (love that word) ways but he still did it, he knew he had you, controlled you and could do anything he wanted to you & with you.
The power in this relationship has suddenly shifted from him to you.
You've taken back control of your life and you're deciding that you want better. He has lost his power over you and it feels like his world is crashing down on him. It's a very typical reaction.
The only thing he has left at his disposal is to try & make you feel guilty and bad for him. He will tell you that he loves you, he was sorry for what he's done, he will also tell you that he will change his ways. He'll then blame you for what has happened, you "allowed" him to do these things to you. He will also play the self-esteem card and say that no one will ever love him like you did, and that he won't be able to find anyone else and that he can't live without you. That feeling of disgust you mentioned is normal, think about it this way: he had full control of this relationship, he was very powerful, in charge, in command, although what he was doing wasn't very nice, being powerful & in command is an attractive quality and once he knew he could use that on you, he kept you under his spell. Once he lost his power, revealed his true nature which was no power, powerless, helpless, juvenile, petty, etc, he lost all of his charisma and it was revolting/disgusting for you to see that. You lost any respect you had for him.
Be careful of the guilt trip he may lay on you, it may work to keep you under his spell and continue his past ways.
I'm not telling you to stop having feelings for him - I would never tell anyone who they can or can't love, just realize that you need to start loving yourself properly and once you do that you can love this or your next partner a whole lot better and the reason being you will have respect for yourself and your partner: self-respect & mutual respect. You will also have gained your individuality back which is so powerful and important.
If this is someone you want to continue a relationship with, let him prove himself. Give him time & space away from you (because you need your time & space now also to determine what direction to take your life in, you're in charge now) to change his ways, to become a proper human being who can love himself & others and provide people with the proper respect, the kind of respect that nurtures someone else's self-esteem, not tear it down and take advantage of it. Don't provide him with any guarantees on the future of the relationship either. He is in control of his own actions & thoughts, don't feel bad for any stupids things he may say or do, it's all him now. You have control only over your own actions & thoughts (you always did, you're now exercising that control).
I'm not saying any of this will be easy.
No one said life would always be easy - on the contrary for some people life can be difficult for the most part. That isn't the important part though, so don't focus on that. The important thing to remember is that life, your life, is worth it. And if you want a better life, a life with less difficulty, make that life for yourself, don't expect anyone to do it for you. The potential for a great life is within you, the only person who can unlock that potential and make use of it is you - it was always you.
Sometimes we just need people in our life to offer a different perspective on our problems and help us look at things from another angle because we can get stuck looking at life with a specific set of glasses on.
I'm rooting for you Faye, let me know how it goes. Be strong, I know you can do it.
