I don't know the ins and outs of custody but I have an idea of what you are dealing with. Look at the website
BPDfamily.com
If he matches up with the symptoms, well, there is a board on there for people just like you. There are SO and spouses of people with Borderline Personality Disorder and are in the same position you are in. There are also lessons on boundaries and communication techniques.
Yeah, under normal circumstances, the Dad needs to see his kid. But I suspect this is not a normal case. I'm sorry. I have a mil with BPD. If there is someone with a chance of having this in their lives I have to speak up, so forgive me if I am wrong.