It sounds like a divorce would be appropriate. Now if you are concerned about his health, you don't have to stay married just for that. You can divorce him and still choose to help him some if needed so that it doesn't all fall on your children. You can choose to do as much or as little as you want to in that regard.
I think sometimes people have to live with the consequences of their choices and actions. If he ends up alone and in poor health, it sounds like he made that bed himself.
Kelly,
Thank you for your advice. Yes, I agree, I do need to leave him. He swore that he ended things but I know he hasn’t, he treats me differently whenever he speaks to her. I am simply waiting until I graduate and know I can find employment, that will happen before the end of the year. Needless to say I am counting days. But, it is nice to get advice from someone who doesn’t know either of us, so thank you.