Welcome, and I am so sorry this is happening to you.
You have searched for answers and your gut-level response is you know your H has BPD. NPD is very similar. In fact, those with BPD can have NPD features.
My uBPD H is the same in many ways. Sadly, I have stayed with my H for 20 years. Early in our marriage, I knew something was "off." My H would rage, call me the worst names and make divorce threats.
The chameleon or "Jekyll and Hyde" aspect of BPD is familiar to many of us here. Ditto for the blaming.
Educate and protect yourself. You know the process of "idealization, devaluation and discard" is the process of BPDs and NPDs. Make sure you have financial resources in the event he leaves. Protect your children.
It's called "crazy making" for a reason. Bear in mind it's not your fault. For whatever reason, likely something rooted in his childhood, your H is unstable.
You appear to know the dynamics at work in BPD. You are not powerless.
