His behavior may be his base line (the level of functioning that is the norm for him) If that is the case, he may not make a whole lot of improvement/changes not because he does not want to but because what you see him doing now is the most he can actually do.
You've shared that you're feeling as though you're taking care of him, which does not show like a partnership where he is contributing 50% but more of a situation you're trapped in.
There is no easy answer as to how to manage your feelings because that would depend on what you want to do (and what you believe would be realistic to expect from him)
You have already invested time and energy into the relationship and there are also the children to think about.
If his medication does not seem to be effective, he could explore other options. There is also the issue of whether what you observe is all as a result of his ADD or like you said a habit of his.
You can decide to give it another chance if you believe that he is capable of improving to the point of where you would be comfortable with his behaviors, accept that this is his base line or leave. Whatever you decide would involve flexibility and compromise in your decision.
If you do not feel in love with him and can not rely on him, then that is another issue. There are times you would have to ask yourself if you are bothered by his behaviors or you're more upset because he is not living up to some image you though he would.