Crayfog,
You've been through a lot dealing with your husband's uBPDx. You were strong enough to reach out here for support with that. That you have other pwBPD in your life is certainly triggering. Though your H isn't BPD, it's likely he has fleas from his exW as
Suzn suggested. It seems like you and he might be triggering each other due to traumas that don't have roots in your r/s specifically.
Have you thought about posting to Staying? The validation tools can work on anyone (I use them with my kids

and going through the lessons there may help give some focus to you (for you) as well.