I don't think he'll get revenge on you, as he will be wanting to look respectable and to carry on with his quiet home life and to minimize the drama. Now she knows, all the responses of the friends and friends of friends/workmates, will come into play, and he'll be wanting to salvage some sort of vestige of reputation - 'a decent man who made a one-off stupid mistake', so he won't be thinking of posting revenge porn or getting aggressive.
Three or four married posters have told you they wish they had known the full facts and the truth about their partner's infidelity. If the wife speaks to you, be honest. If he's a serial cheater, he won't want to stay with you anyway. You know you wouldn't have exclusivity with him, and she knows that you know that, and she will probably believe what you tell her, if you tell it in a straight way, as you've said things on this thread. She,'ll see you are not trying to put her off so you will get him.
I think knowing he is a serial cheater and not a foolish and mid-life-crisised man will help her to stop feeling sympathy for him and that would be a good thing if staying with him were to diminish the joy and self-respect she deserves. But that is for her to decide, how she responds.
If you want to decide, respond specifically to those posters who say that they, or their mothers, were the wife and knowing the truth and the lies helped them to move on. They know - not we others. Ignore the responses of those without the experience, but ask more questions of those who are engaging by channeling their own perspective.