I think you've had a bit of a hard time OP, though I agree with everyone else that it is a whole golf course full of red flags - and really, as others have said actual incidents not just flags!
I am an intelligent, independent (practically, emotionally and financially) fairly ball breaking woman.
But I look back and I am AMAZED at the shit I put up with from my XH because there wasn't actual evidence, or could have been another reason.
How many people really would leave their husband if they found out he had looked at Tinder but swore nothing had happened, he was just curious what this new site everyone was talking about was, and his mate had met someone on it...
I mean, in retrospect it's total bullshit but every time there is a plausible excuse, or even if not very plausible, there's the outside chance it could be true.
Here's my best one: my XH got a letter warning him that he'd been seen driving slowly several times round X streets, and that it was an area where residents had a problem with street prostitutes. A warning letter that the police don't need "evidence" for. I found it 6 months later. His explanation? He was circling slowly waiting for a parking space outside KFC to be free - didn't want to park his expensive penis extension car anywhere but out front cos it's a rough area.
Now, everyone on this thread would scream - are you THICK?!! Turns out, he was indeed an avid user of prostitutes, and I later had plenty of evidence. But you know - I'd actually been in the car once before when he had done exactly this!
To this day, I'm not 100% sure which was the truth! But I expect everyone here would say "FFS - it was the prostitutes!" My best friend certainly says it.
But what people don't get is it's hard to reject an explanation if it is possible, it doesn't have to be probable.
In my case for that incident, add in that I had a 4 month old baby, who woke 8x a night and I was barely functioning!
So look, my point is...
It's OK that you missed the flag, made the wrong decision. Why beat yourself up? It doesn't help.
Just remember that it doesn't matter if something was a year ago, 5, 20. You're still allowed to act on it NOW.
We try to justify divorce to ourselves, with perfect evidence.
You know, it's actually perfectly OK to say "many years ago you said men needed more partners than women - that's shit, I'm so over this, I'm dumping you".
You don't have to justify it to anyone.