Moving on is so hard, but may be necessary. Try joining Al-anon. There is lots of help for you there.
I think its time you became fed up with his behavior as well. You are allowing him to act and treat you and your children this way by holding on. Whether he is using still or not, why would you continue to put yourself through this hell when you can do something about it? I suggest you go to alanon and learn how to work on YOUR side of this disease. As you said, his addiction has affected the entire family and everyone needs treatment for that. If he's not willing to get it, or stick through it, at least you can do your part and get yourself healthy-emotionally and mentally. you DONT have to live like this anymore. He is obviously choosing drugs or another way of life over you so you need to move on.