I think men who look at a lot of porn give off a "vibe", whether they mean to or not. It was in my WHs eyes - I recognize it now because it's gone.
Anyway, I'm sorry you have to go through this. 20+ affairs is an awful lot to process. I am quite sure I would be completely beside myself in your position. Gently, you cannot lose yourself in stress and worry over what he is going to do or what opportunity he is going to take. It is so infuriating when other women are so disrespectful, but he is the one who needs to be giving the "step off" look to poachers.
The woman only left because you gave her the death stare. On e you were gone, your H again appeared available for conversation.
Not saying he does it intentionally, he may be the friendly type. But given his title of WH, he needs to work on being less friendly with women when you aren't there to introduce.
I was a girl who was an epic flirt. Never met a stranger. Batted my lashes at anything in pants. I could tell in 0.2 seconds who responded to the vibe.
In the aftermath of Dday I realized quickly who the problem was. Me. Locked down the boundaries. And shut off my "Yo hubba hubba" vibe. There is a difference between friendly and friendly. Focused on my husband. He became the object of my attention and flirtation. I'm so far off my game now, I couldn't flirt if my life depended on it. I just state the obvious for him and he's cool with that.
Maybe your husband isn't emitting vibes or looks or whatever. Some people are true idiots and wouldn't sense a roadblock if they totalled their car into it. That's when your husband has to step up and be an enforcer. He puts his arm around you and makes positive "we" and "us" comments. Or he flat out tells her to talk a long walk off the short pier her husband is fishing off of.
I'm sorry she triggered you and I hope your husband handled it correctly and is doing what it takes to fix himself.