Teke, it sounds like you are afraid to be alone. If you can't do it for yourself, do it for your children. If you can't get him to leave, why don't you move out somewhere else? I know it is sooooooooooooo hard to let go, even when there really isn't anything to hang on to.
I hope you have a sponsor, go to some Alanon meetings, and get some local support. They will give you the strength to become your own person.
When you are on the crazy train for so long...it is so hard to get off of it. The jerk is cheating on you, call his new GF and ask her to take him in.
Life is too short to be wasted on someone who is to far into his addiction to give a damn. Big hug.