Hi bookworm1,
I just don't know where to start with this process.
Here is a good place to start
Have you tried validation with your kids? I know we often talk about using it with romantic partners, but your kids may be really starved for validation and respond in positive ways, building your skill set.
People with BPD tend to a bottomless need for validation and are extremely invalidating to their loved ones. There is a good chance your kids feel emotionally alone if their father invalidates them. Do you think that's the case?