DON'T IGNORE MY ADVICE. Believe it or not, I'm actually helping you.
I had to answer this question and spent a lot of time thinking about it because it really touched me. I'm not going to be condescending because I really feel for you. Love can hurt.
I fell for someone unavailable and I did nothing about it. I knew he felt the same about me (he made moves towards me but I always snubbed them) but I also knew he was never going to leave his fiancee because with her, he had security, a future and a true soulmate. It was a relationship based on long-term mutual respect. I was new and exciting (I'd been in his life for 2 years) but far riskier- and those kind of feelings fade. I told myself I had to move on. I haven't quite moved on but after nearly a month I'm getting there. Now he's moving abroad and I'm fine...that's what a lot of these kind of men do. They show they love you and then they leave you. Don't kid yourself with this man, he will leave you in some shape or form, and he'll leave you incredibly vulnerable to new relationships.
No matter how interested he looks, at the end of the day he is entangled in another relationship- a marriage. Which is far stronger than any fling- and he knows that too. He'll never leave his wife because leaving his wife means leaving a whole life, friends and family and he's probably learnt to keep away from you. The crying and guilt said it all. Even if you can get him you can't guarantee he'll be faithful to you.
I know you don't want to hear it and as heartbreaking as it is you have to move on otherwise you risk further heartbreak and loneliness. Tell yourself that you're worth a guy who is willing to give you all of his heart and soul into a monogamous relationship. It is possible. Put yourself in his wife's shoes...she probably loves him and in her 40s or 50s (presumably) she may not get a second chance at love, unlike you. Don't be a bit on the side, treat yourself with a bit of self-respect (that's the only way you can avoid being called a slag) and take a holiday as soon as you can. It'll give you enough time to at least move forward away from the married man.
Personal experience - don't tell yourself that you're situation is different. It only feels different because it involves you.
Books- 'He's just not that into you' - a frank self-help guide which would tell you that this kind of relationship never works out especially from the facts you've given us.
All the wronged women and children in this world whose lives have been ruined because of cheating men- this kind of relationship hurts everyone and affects more people than you think.