She's the department slut? (Ok, not into slut shaming, but what else would you call a woman who has slept with every guy in the department? She's either a predator or someone with NO self esteem. )
No matter what you think she has on you in the looks department, your STBX already made it clear to you it wasn't about your looks. Whatever you are dissatisfied with about yourself, it wasn't the cause of his infidelity. (But now is a great time to fix whatever you want to fix, btw.)
It's true, they mostly affair down. Even my ex's new wife - who thankfully was not one of his affair partners and I have nothing against her - I'm sure he had to adjust to being with someone who plays the little girl and isn't terribly intellectual. I'm sure that appealed to him at first, but I can imagine now there are days when he tires of being "Big Daddy". And she's got a guy who is 19 years older than her and starting to rapidly show his age, with multiple health issues. He has to worry she might leave him or cheat on him, and if she's ever discovered his history of cheating, she has to worry he could cheat on her. Him leaving me had everything to do with him and his inherent unhappiness and next to nothing to do with me. He's not happier now, by any measure I can see, since real life intruded on his fantasy of being young.
Your OW has to live with the knowledge that he could cheat on her too. And your STBX has to worry that OW could find another guy, with her history. I wouldn't want to trade places with either of them and neither would you.
The best revenge is living well. Focus on achieving what you want in your life and let him follow his path. You can't save him, he has to take those steps himself.
Oh - another great 80's movie to watch - She Devil with Roseanne Barr. Her husband leaves her for a simpering Meryl Streep, and she transforms her life into a huge success while destroying him bit by bit. Yes, it's a revenge fantasy, but pretty hilarious. Helps to vent those dark thoughts sometimes!
