Hi Joro,
I can relate to what you are saying. My BPDh has been on medication for about a year, and there was a time in therapy recently where he acted like I was exaggerating or making up things about his past behavior--particularly his delusions and borderline psychotic behavior. Last year I made a long list of all this lies and all the things that happened. Other people thought I was being obsessive by doing this, but it was very important to me to have a list that I could use for reality checking.
My therapist is always helpful at directing us back to the feelings so we stop arguing over the facts of events (accepting that memories change and everyone's memory of the same event can be different). It's so validing to have someone else say, "But BPDh, you DID frighten LR. You HAVE done things that hurt her."
Seems like he is either being very deliberately cold and typical hurt them first/more (but without any show of emotion) OR has really been scary evil and faking bpd all the while and let the cat out of the bag while on meds, like drunk truth.
I remember having this thought in the past. Like he was some evil mastermind purposefully trying to manipulate me to some awful end. But the reality was that while he was manipulative, he was also spinning wildly out of control.
I hope if your BPDh won't do therapy at this point, that you might consider it for yourself. A combination of medications and psychotherapy is the best way to treat most MH disorders, in my understanding. Your husband might be feeling more stable and less out of control right now, so it might be easy for him to dismiss past behaviors. (Or even protective of his ego to forget that it happened.)