Hi, Ontheriver

I'm sorry to hear about your suffering, I know mothers suffer double when a small child is involved. As in "I can take whatever, but I have to protect my child". At the same time you love this man, and you see him suffering and would love to take his suffering away, also.
You've been already reading about this (Which books?) So i'm sure you are familiar with many concepts already, check out the lessons on the right, even "veterans" need to refresh the basic concepts often, as common sense often lead us in different directions, and we forget what works and what doesn't in our situation.
I'm no doctor, but sound like he felt threatened by the illness of the girl. Even as they know it's wrong, they could feel abandoned when your attention goes elsewhere. It's not a rational thing, it's an instinct, they could be very angry at a person that dies, for leaving them (We understand this in a child, but not in an adult, but it happens). More importantly, he gets the idea that you are going to talk more to your ex. And having in mind that he thinks about himself that he is notihing, not worthy of your love, of course you are going to fall in love with your ex again and leave him. It's paranoid... .But it's absolutely real for him. And it hurts as if you alredy did that. When they can adknowledge that it's all in their heads, they feel ashamed of being so "damaged", they will cal themselves "ridiculous, crazy, nuts... ." and worse things. That tells them again they are unworthy, and the cycle starts again.
I hope you can tell us a little more:
- Is he also thinking it's BPD or he's feeling "somehitng is worng with me" but he doesn't know what? He sounds intelligent, do you think he could benefit from knowing?
My Gf is also the quiet type, and she's making progress on her own, as DBT is not available where we live, either. Sh e was hurt by the diagnosis first, and scared... .But after a while, it was very positive to know that there are things to do to improve. He already improved by quiting drugs and alcohol, that's huge, and it was a defense mechanism for him, a way to avoid the pain, that he now doesn't have.
- Do you know about his past? How's his relationship with his family of origin?
- How was his relationship with your daughter before this incident?
- Has he been jealous before?
Check out this lesson about jealousy:
https://bpdfamily.com/message_board/index.php?topic=78324.0What do you want about this relationship going forward?
Going through the bocks, to me there are some concepts I don't wholy grasp, but I got them better after reading examples by members here. Do you have any doubts?
We are here to listen, and we've been there, we are there. There is hope. I hope we keep hearing from you.