Seeing all that online was, in essence, being rejected...again. It's natural to experience it as an personal online rejection. It's not really, but I know that's how it feels.
That's why you gotta be really, really, really, REALLY careful with snooping. It's easy, when your are feeling rejected/being rejected to take things very personally and integrate the rejection into your soul.
LOOK AT THE FACTS:
Go back to looking at Mr. Middle-Aged, Sexually Adventurous with the eyes of a scientist. Since, like me, you can't seem to quite processing it...over and over...:-)
Is he a great catch right now? Seriously?
Take a balanced, sober look at this man...with ALL HIS QUALITIES, good and bad.
You've mentioned he isn't capable of having a real relationship right now. You mentioned he has a problem with porn. You mentioned he is, generally, being a big dick to you. So, IF, he finds someone...what are the chances she will be Movie Star Beautiful and Super, Duper Awesome??? Um. No. She will be very flawed to accept a dishonest, married, middle-aged man with some fairly obvious sexual issues. Ewwww.
Did you ever see The Incredibles? If not, google the scene where Edna Mode slaps and, then, tells Elasti-Girl..."Pull YOURSELF TOGETHER! YOU ARE ELASTI-GIRL!"
"You know, it's times like these when I realize what a superhero I am." Tony Stark/Iron Man
“Focus on what you can do, then do it with all your heart.” Lois Wilson