I read your posts and felt absolutely horrible for what you are going through. You did say one thing that stuck with me. You mentioned he got divorced 5 months ago and it wasa nasty one. The questions I would be asking myself are:
Did he dive into a serious relationship to quickly and is emotionally and mentally unable to be a full-time partner to you?
Was he using you and other girls to help lick his wounds after this divorce? Cancers do not handle loss and rejection well.
Is his marriage truly over? Not in a physical sense but again emotionally and mentally?
You mentioned several time the age difference between you two. Why is this such an issue in your mind? Plenty of couples manage this just fine.
Was his cheating a way of telling you he simply can't do this right now? Clearly he does not want to be the "bad guy". What happened in his marriage? Cheating?
Don't get me wrong. I do not want to sound sympathetic to him as I'd have sent him to the curb after the cheating. It just seems that you are looking for answers. It sounds to me that you fell for someone who is desperate and not particularly stable.
Love is not betraying others to meet our own selfish needs and feed our fragile egos. This guy sounds weak to me. Why would you want a relationship like this? He doesn't even have the courage to face the cheating. This is not a man. He's a little boy and you deserve better. I have been in your shoes before and believe it or not I am better and happier for it! I now know what I want and what I will put up with. Ride it out as much as it sucks. I wish the best for you!