My husband of 12 years has bipolar 2. It may help you to know that with proper medication,  this is a treatable disorder. 

My husband was diagnosed about six months after we married. I pushed him to see a psychiatrist and get diagnosed. That was easier during a depressive period, because the highs were too fun for him to want to give up! And the mixed episodes (like agitated low moods) were too ... agitated.  

It took a while, but with his psych he found a good mix of medication that smoothed out the extreme highs and lows. There are still hard days sometimes but the good days out number them and i know i can help him cope with the bad days. He's also gained a lot of insight during those years, and life is nowhere near as rocky as it was. I nearly gave up in that first year, but I'm glad i stuck around. Definitely not saying our situations are the same or that you should change your mind. I just wanted you to know bipolar can be effectively treated, if he will agree to it.