:hi:Betterlife, and welcome to the family! I am so sorry for what you are going through! We are here and will support you through this. You are in a good position, your partner has been diagnosed and is in therapy. Those are usually good preconditions for things to get better.
My first relationship of 16 years, my partner regularly broke up every six months, triggering all my abandonment issues. If I had known then what I know now, I would have dealt with it much better. Try to see it as an electrical storm that passes through their brain, they will say anything and it doesn't have to make much sense.
Are you in therapy? For one you will need support since the process of healing is a time of great change. And for two, yes you will have to change too. Not necessarily according to your pw BPD suggestions, but it does help the relationship if you can become stronger and wiser about how to handle the electrical storms. Here's a good place to start :
https://bpdfamily.com/message_board/index.php?topic=42176.0