Stiney, welcome to the forum!
You are a kind and loving wife to want to learn about your husband's BPD diagnosis. The diagnosis is the first step, and your husband wants help. As you noted, sometimes people with problems have to hit the "bottom" before they are forced to seek help.
"You always hurt the one you love," that line from a song, is very true for the spouses of pwBPD.
You already know the splitting/Jekyll and Hyde feature of pwBPD. Realizing the incidents in your marriage were actions of a BPD must have been like a light bulb turning on.
You will find many resources here on communication techniques with a BPD spouse.
I hope they help.
https://bpdfamily.com/portfolio-4-colsLet us know if you need help or other suggestions. Keep in mind that your husband has asked for help, and that is an enormous step for a pwBPD to make--and you know that.
It is not easy to be the spouse of a pwBPD, but learning how to navigate communication is very, very helpful.