Veggy, I'm sorry for the stress, pain and emotional chaos you're experiencing. Though only a doctor who sees him in person can diagnose him, based on my personal experience he either has a mood disorder or an addiction problem or both (could be self-medicating with alcohol or drugs.) Either way he sounds like a danger to himself and to anyone who is close to him. It sounds as though you need counseling to cope with ending this relationship and moving on to a healthier relationship. Unfortunately you can't help him if he is unwilling to get help himself. You can suggest, as a friend, that he seek help but based on my experience, men are resistant to psychiatric help unless they are forced to through a job or in a crisis.
As someone who has been involved with men with mood disorders and substance abuse issues, please get help for yourself and move on. You'll be saving yourself years of abuse, pain and an emotional roller coaster.