Seems like you have already laid the foundations for remaining friends, as you accepted help from him yesterday . It would seem a bit harsh after doing that to then turn on him (but could be a good way of saying "fuck you" if that is how you feel ). Ideally, you should have severed all ties straight away or stick with a decision to remain friends with him.

A difficult one and maybe worth talking over with your sister to find out how she would really feal about you remaining friends with him (taking time to explain how much your kids think of him as well). She may understand and accept that he has done nothing to directly hurt you, if so and it is a friendship you feel is worth something then keep it. If not and your family's approval is something that is more important to you, then all you have to do is to explain to him why you will have to terminate the friendship. This will probably make him think about his actions more than hitting him (as being a bouncer he is probably pretty used to taking a few punches and will forget about it almost instantly). His loss of you as friend will hurt him as much as you by the sounds of it....