Unfortunately, some people do use their mental illness as an excuse... I don't know him though, so I can't say if that's the case here. What I can say is if he is destroying things and verbally abusing you then you have every right to want out. It could turn physical, but even if it never did that's a miserable environment for you to be in.

You haven't mentioned what he's doing to stop this behavior, but if it's been going on for 3 years, whatever he's doing isn't enough. If you love him and want to try to make it work you can try talking him into getting more help. Maybe medication is something he needs. Maybe you can help him find resources online that he can use to self-help if therapy isn't an option due to how difficult it is to get into over there.