Wow, that is a tough situation. I guess there is really no right answer here. If you stay in your marriage out of duty you really aren't doing your H or yourself any good living a lie. And if you leave because you are in love with this other man, there are going to me some hurt people as well.
I would see how the T goes and if you feel some renewed love for your H. Maybe tell this other man that you need 6 months without any contact to see what happens in your marriage. If you were meant to be with guy #2, he will still be there waiting for you Im sure.
But I wouldn't drag this out too long for the sake of your H and his W. It will hard enough on everyone anyway.
Any kids? That makes the decision much harder because you have to think of their well-being as well.
Hope this helps you a little and I wish you much luck and happiness.