I know this has to be heartbreaking and leaving you in one hell of a position, in not knowing. And that is where I'd draw the line. There is no way in Hell I'd let any man do to me what your SO is doing to you. I understand he is in deep stages of grief...been there myself...but that did not turn me away from my husband.

Personally, I'd change the locks, pack up his stuff and put it in a safe place for him to retrieve. I don't know how you can come back from this...unless he'd be will to do some serious counseling and set some serious boundaries with his family and that ex of his. 

Please...get yourself into therapy....call a crisis line if you need to talk with someone (I did that type of volunteer work before. It was a rape crisis line but we talked with anyone who was in any type of crisis). You need to focus on YOU and healing from this disaster of a life event. Sending you love.

Please reach out to people you know irl who can help you get through this. What your partner is doing is not ok and you should not accept this treatment. You deserve better than what he has given you for years. Nobody deserves this. He won't let you support him. Use the strength you wanted to give to him on being a support to yourself. You waste all this energy on someone who has disrespected you for years. You can pour this love and support into your own life. 

This is on him and is not on you.  Have you rekeyed the locks yet and closed and moved all moneys to accounts he is not on and does not know about?  If not, do it. You have to move past victim/grief mode and effectively protect yourself.  Engage in your grief and recovery after you lock down your self protection actions.

Yes, what you say above should be how it happens. But it can't because he has proven himself to be unworthy to be your partner.

IMHO of course.

Take care of  you.

My heart goes out to you. Please surround yourself with people that care about you, even if that's the last thing that you feel like doing. You don't have to talk about your problems - superficial conversations, or even physical activities are enough. Help someone move house, do some gardening for an elderly neighbour, or even offer to volunteer at a local community event, if you don't have anyone close. I promise you, being around other humans will eventually start being bearable and you will start feeling better. Every grief has beginning, middle and end. You won't be in this state forever. 

And above all, make sure you have food in your fridge and eat as well as you can, even if the very thought of food makes you feel nauseous.