The mind set that it is "all your fault" only shows he is in a very skewed place in his head. He is crying out for help. Can you arrange some counseling for him with his participation?

Sounds like work is a big factor, and some perception of your relationship that is off kilter and clearly there is something he is not telling you. He needs help to sort it out and stop blaming you. He said he feels he is breaking down, so is he able to take a sabbatical?

In the meantime, focus on getting through this final step in your degree. It is really important for you to do this for yourself.

Best to you ...