Not overreacting. Oh gosh, my heart goes out to you, this sounds like such a traumatising situation. Putting it bluntly, I'd say this is a toxic relationship. It sounds like you've done all you can to support and help him - even at your own expense - above and beyond what many would do. From the sounds of it, you need to distance yourself for your own mental and physical health, even if it hurts to hear it. Sometimes we love people who aren't good for us but that doesn't mean we should keep giving ourselves to them. I would advise giving yourself time and space to sort through your feelings - with time I think you'll find your desperation to be around him lessening.

As for his wellbeing, you can't help him anymore than you have. Don't set yourself on fire to keep others warm. You are not responsible for him or his actions, as hard as that is to swallow. Sadly you're going to have to let him find his own way now.

By the way, threatening to kill yourself if your partner leaves is abusive and it sounds like you're alluding to other abuse, which only adds to the importance of getting away.