Why? Just why can't I tell him there is nothing more to do or say about our marriage? Why can't I get the words 'it's over' out? I am very confident and have had a moment of clarity where I know he can't get better.
I don't know you or your relationship. I only know my own past BPD relationship, so I'll tell you why it was hard for me... . and maybe some of my experience will ring true for you.
The way I related to my xBPDgf was not adult to adult. It was more like child to adult. And in the beginning when I was falling in love, it was like we were both children. But over the years, I related to her as a parent to a child. I worried about her (too much). I did not have confidence in her (over some things). And I felt obligated to her, like if I left her she would be in some kind of distress. It did not help that she would reinforce these kind of thoughts. She told me how much she *depended* upon me. She made me feel bad whenever I placed any other obligation or responsibility ahead of my obligation/responsibility to her. Even though she was an adult woman, I very much did not relate to her as such.
And when she was in a dark place, I felt that if I loved her enough, she could get through it. Even weeks after she dumped me flat on my arse, I was more worried about her and what she might be going through, than I was about my own distress. It was a sobering realization. For months I kept expecting her to fall apart and run back to me... . except she didn't. The only person who saw her as a wounded child, was me.
It is hard to "abandon" a wounded child. Especially if that "child" keeps screaming "don't leave me!" But the truth is, they are not children. They are more than capable to seeing to their own needs than we are able to so, than they are willing to admit, even if the means by which they fulfill themselves is not healthy.
Do you see your husband as a capable, resourceful adult man who is capable to taking care of himself if you should leave him? Are you willing to put your own emotional needs ahead of his, just this once?
Maybe you aren't willing to give up the "idea" of what marriage means to you? That if you say "it's over" this means you are giving up on some ideal that you've always believed in? Well I would argue that whatever that ideal is, he failed meeting that ideal long before you ever considered giving up on it.
He's threatened divorce our entire marriage. Is it just timing? Is it fear of the unknown?
He's threatened divorce your entire marriage because he has a disordered fear of abandonment. Abandonment is what happens when you are left behind, not when you leave. If he leaves, if he abandons, then he's avoided his fear. If you make the choice, if you "leave" instead of him, then this is his fear.
If you make the choice, then you can go under your terms. If he makes the choice, then I fear he will not be nearly so considerate as you.
Best wishes, Schwing