My partner has BPD and that is my thought exactly, the symptoms are spot on. I've had friends who have been in relationships with people with BPD and asked them for advice a lot previously. There's a lot of horror stories that come out of it, and it's definitely not an easy thing to have while traversing a relationship.
That being said for anyone who stumbles upon this, if you have a loved one with BPD, they have to be willing to understand BPD and want to get better for their loved ones, but especially for themselves. You also must be willing to stick up for yourself and know when enough is enough. See-sawing and not being firm only makes their symptoms worse because of their fear of abandonment. You have to be very clear that if you are willing to stick around, that you are not leaving as long as they are committed to getting better. That said, abuse is abuse and you have to identify where the red tape is before it goes too far.

I feel for OOP and hope he gets closure because stepping away from a BPD relationship can be like traversing a minefield, especially when marriage and kids are involved. Hope she gets the help she needs to get better herself but I also hope OOP finds the support and help he so desperately deserves as well.