Welcome red. You're right that he needs to see a doctor, ideally a Psychiatrist. I will say that your description does sound like bipolar, but bipolar can share symptoms with other mental illnesses and this is why seeing a Psychiatrist is so important.

Your needs are important and perhaps by explaining that you're concerned and will support him, but you're not willing to tolerate abusive behavior. Perhaps by setting a time limit on him getting professional mental help will help protect yourself. The book in my signature is for fiends, family etc. of those diagnosed. It's excellent.