For the last year, I have been focusing on myself, before the BPD knowledge came to light. The knowing is just a bunch of terminology and justification. Nothing has changed except the awareness that I can now give the insanity a name. But perhaps that's just what I needed to know that change, if ever possible would be a lot of work. I am all worked out. Exhausted. And now I need to take care of me so I can peacefully become the person I was meant to be. There is a light coming through my prison door. I am fearful that my "escape" will not be met with any rationale.
This is a difficult time in any relationship - you are married, living together 20+ years, have 4 kids, and you have detached and plan to leave. He is certainly picking upon all of this.
Have you thought of taking a supervised therapeutic separation? Getting on the same side of this might resolve the conflict and be good for the children.
I noticed in an earlier post you said your husband has 20 of the 30 signs of BPD... . I don't know of any 30 point list and it may take a little more digging to know if this is a personality disorder or just a long built up relationship breakdown.
Nonetheless, the relationship you report sounds very very contentious at this point. A supervised therapeutic separation is a good stepping stone. If brings peace pretty quick and whichever way it turns out helps. If you conclude in the process that its divorce, this is an acceptance period with therapy assistance. If you conclude in the process to try, this is an decompression healing period with therapy assistance. Therapeutic separation is typically 6 weeks with rules to make it safe and milestones to achievement.