Agree with the diagnosis thing... there is more to BP than a list of symptoms, and meds can and do help!
what you read here on this forum does show the difficulties of getting the *right* meds, but also understand that the people who post on this forum probably reflect the more serious end of the spectrum, eg treatment resistant etc.
In the end, it is his choice, you can encourage and support, but he has to want to fix whatever is wrong, be it BP or something else. He is the one who will have to live with the diagnosis, take yucky meds, live with side effects and/or go through difficult therapy...
Your choice is how to respond to his behaviour when it is inapropriate or unacceptable. I agree with blue october that you deserve to be treated with respect, regardless of whether his behaviour is due to BP, another illness or his personality, it does not make it acceptable to treat you badly.
It is important that you do not take it personally when he treats you like this, it is HIS problem not yours, you can only change how YOU respond.