Divorce is a debilitating experience. It will change you, forever. Your marriage is less than optimal. Are you prepared to have most of your possessions sold, cheap, and the proceeds divided? That's the financial reality. An affair is difficult. It's expensive, and requires a lot of work, planning and forethought to keep from being exposed. I don't see how a discrete affair, at this time would be that "wrong". Those that criticize you, have never been in your situation. They are not qualified to even comment. When these ignorant, uninformed, people criticize you, they are worse than the "sin" they accuse you of. Make your own decision, based on YOUR OWN situation. Not the advice of a bunch of immature kids living in a fantasy world.
As I get older, I find I regret NOT doing things, a lot more than anything I ever did!!!!!!