Your question was how to get out of that relationship. Not judging, just saying if you want to save yourself from a life of misery, walk away from him and don't look back. Move to a different state. Change you phone number. Even change your name if you have to. Life is to short to live it in that kind of prison
It is not advisable to have a relationship with a married man. Get out of it as fast as you can. You can change your line so that he does not reach you or move to a different state. Alternatively, just face him and tell him that you are no longer interested in that relationship.
There is no answer for you. You should simply serve as a cautionary tale as what not to do in the first place. You should pay the penalty for wrong doing. Break it off, accept the penalties, don't make the mistake again.