Yes, this relationship appears to be going no where good. He has gone back to his ex 3 times now. That is not a relationship you want?
He is untrustworthy, unreliable and is not doing anything in your best interests. He is just looking out for number one, himself. You deserve much better than this in any relationship.
I hope you will get the book dandylion mentioned, you will probably find it very helpful in maintaining your boundaries.
Perhaps taking some time to take care of yourself and spend the energy you have been spending on him in taking care of yourself and what you want and finding out what your interests are?
I have to ask, what is a "non-violent domestic"? He got put in jail for yelling at her, threatening her?