There are two separate issues. You should consider them separately.
1) You should consider seeing a therapist for yourself. You have said that you are threatening "self harm" and that your mental health is suffering. It sounds like you are struggling with depression. I do not believe that your partner is to blame for mental health issues.
At worst, it would be healthy for you to just leave him. You still have to work on your own mental health.
2) The relationship is a separate issue. Either you can accept his behavior, or you can't. If you can't accept his behavior then you end the relationship.
It isn't healthy for you to confuse mental health issues with relationship issues. We all have relationship issues... and if they are bad enough we move on.
If you are suffering this much, you should end the relationship
. Take some time to get yourself to a good place before starting a new relationship.