Hi Puffing orca
Welcome to bpdfamily and thanks for introducing yourself.
Being raised by a BPD parent unfortunately often takes it's toll on people. It is positive that your SO is at least in therapy, how long has he been in therapy now? Are there any specific areas you feel he doesn't want to get into?
I can see how him becoming depressed would also affect you and your kids. How old are your kids and how does your SO generally treat them?
We describe several communication techniques on this site that could potentially also help you with your partner. I've selected a few resources for you:
Communication Skills - ValidationEnding the Cycle of ConflictS.E.T.: Support, Empathy, TruthI hope you'll find this helpful.