op, there are and will be plenty of women on here who will tell you that they started out as the ow and that they are now blissfully happy x amount of years on. But read what they have to say carefully. all of those women talk about how they regret the way their relationships started. Is that the kind of new start to your life you want? One full of regret?
So often people will ask couples how they met, and it should be with fondness that one looks back to the beginnings of a relationship, not with regret and sadness over the devastation caused to someone else's life.
I don't buy into the statement that marry a mistress create a vacancy etc, affairs are rarely black and white and many people who cheat on one partner will never do so again. But the breakdown of a relationship is hard enough as it is, it is much, much harder when innocent people are hurt to achieve the goal of happiness.
Anyone has the right to end a relationship. And I would even go so far as to say that anyone has the right to end a relationship because they have developed feelings for someone else. However, it is the overlap between being with that someone else and ending a current relationship which is wrong. And it doesn't matter what the reasons are for the affair or how much of a bitch/bastard the ex is, the affair still isn't justified, even if it can be explained.
I grew up in a town where affairs were common place. And everyone knew who was having an affair with who, and many of these people simply walked out of their marriages and into new lives with the om/ow. And many of them are in fact still happily married twenty plus years on. but even after all that time, people who know them still remember how those relationships started. So even if the couple are now happy and have good relationships with their children and in some cases even their ex's, those people still remember how those relationships started. We all deserve to start a relationship from a position of freedom to be in that relationship.
If this man is meant to be with you then he will leave his current relationship and in time, you can be together. But in the meantime, you have rightly walked away from an untennable situation in your own marriage, and you have the right to be happy. And it may just be that this man was the sign you needed to realise that you were in the wrong place and couldn't do it any more. and that's ok. Now is the time to focus on you and for him to come to his own conclusions. But don't hold out for him, he isn't the one yet, if he is, then it will happen in time, but meanwhile there are other decent men out there who are free to be with you.