Although I can't understand your exact situation I do understand the feeling of 'walking on eggshells' and it's not fair to you. If the relationship is that unstable you shouldn't be afraid to rock the boat a little harder to try and get things under control.

I agree that he needs to get professional help and once that is started you could start attending so perhaps he can get an objective view on how his behaviour is affecting you.

Regardless of this you don't have to put up with this just because of his mental condition. I have severe depression and I know it makes me hard to live with sometimes. But I also know when I'm out of line and usually take some time to sort out my thoughts and apologise.

Don't live your life walking on eggshells.