Sorry to hear you're going through this with the kids too.
This used to be my wife's go to. I typically didn't speak to anything unless I knew I was right or educated on the subject, so she would label me as the god, know it all, always perfect and always right, because, well, I was right

. No matter how much I tried to tell her I was on her team and just trying to help it didn't work.
So what did work? I just stopped speaking to the things about trying to help her. I only tell her when she asks me. These pwBPD are adults too. Let them figure out the right and wrong things unless it affects you. If it affects you, simply speak to how you feel, not what they are doing is not the "right" thing. Even if someone was always objectively right and gave you advice or their opinion frequently (frequency tolerance will be different for different people. maybe your wife can only handle a few instances while you are more pragmatic and open to hearing correct opinions), wouldn't it be tiring? Make sure you're honest with yourself if you're being "right" too much. I know that I was and once I stopped I never had those problems and she would come to me asking for advice when she needed to and we would both be happier for it and we could be on the "same team" when trying to figure out what was right. The disordered thinking and realities of pwBPD typically have a kernel of truth to them, you will read about that on these forums.
Try to look at yourself and be accurate about yourself. Being right or accurate isn't working, so what do you think would work for your wife? What has worked in the past?
Regarding the past and what you say "When I express my sense that she's defending her behaviour in ways identical to before she regained control of her life, she deflects. She says I'm stuck in the past and that I refuse to acknowledge her progress." maybe instead of pointing out her bad behaviors, you could frame it as a story of both of your struggles in the past and remember how it was good when she did X or Y and how helpful it was to the relationship. I think this would validate her progress while acknowledging that better behaviors she's already capable of need to come back into your relationship.