Hello Lostforwords28, glad you found us and reached out

Your situation of "two years amazing, then sudden pivot to horrible" sounds so familiar. The good times can be really good, then the bad times... like you're describing, the bad times can be devastating and punishing.
Couple of thoughts I'm having as I read your post:
-You mention feeling stuck after having invested everything in your marriage. That's relatable here -- a lot of members have been in similar situations. Can I ask, are you wanting to try to reconcile or save the relationship, or are you ready to be done and detach? Or somewhere in the middle? When we learn more about your goals, we can move your post to the board with the best fit (for example, we have boards on
"Bettering a relationship",
"Conflicted about continuing", and
"Detaching from a relationship") where you'll get targeted advice.
-I'm also seeing you wonder if it'd be helpful to try to convince him that he has BPD. That's a tricky area. I'm with you that the world would be a better place, and people would be in less pain, if pwBPD would seek out and stick with treatment. Anyone would want people with MH challenges to heal. The difficult issue with BPD and BPD-type behaviors/traits (whether diagnosed or not) is that BPD is a shame-based disorder. Telling someone they have a stigmatizing MH issue can create defensiveness and resistance, a sort of doubling-down on "I'm not the problem, you are", instead of an openness to hearing more.
In fact, we have a great thread on that very topic here:
Telling Someone You Think They Have BPDCheck it out and let us know if any of it resonates with you.
Looking forward to hearing more from you, and again, welcome;
kells76