It tends to go against the grain on here, but I'm very much of the mind that you don't meddle in other people's business.
OP it sounds like there's a little bit of "If I can't have him, she can't either" going on here in wanting her to know (though appreciate you've said you won't tell her).
There's a C-suite guy I work with that was having an affair with not one, but two junior colleagues. Another colleague took it upon themselves to rat him out, and all hell broke loose. Both women ended up having to leave the organisation and the man somehow emerged from it with only minor scratches on his reputation, marriage still somehow intact, and is now on to the next target (eww). He tried it with me at a works do not long ago, and I laughed so hard at him I almost spat my drink all over his designer suit.
The world isn't kind to the women in these situations - OW especially, but wives too, as they are looked down upon for staying, but in reality often do. This guy's wife is a SAHM/influencer type, and I'm guessing her own earning potential wouldn't run to the lifestyle she currently has, we're talking private schools, spa weekends, and certainly not that amount of extensions, Botox and fillers. She was never going to let him run off with a junior manager, and if she's stayed purely to make his life awkward and ensure he continues to fulfil his commitments to his family, well, there's some strength in that I suppose, even though she's not my sort of person.
Married men are a thing to stay well clear of, and I would be blocking him and anybody connected with him so you aren't tempted to check. No contact is what's needed so you can properly move on. And some therapy to figure out why you ended up with this man and accepting the scraps/being discarded when it no longer suited him.