This is so similar to the shenanigans I caught my fWH in ten years prior to his physical affairs. If you click on the little person icon in the upper right of this post, you'll find more about it in my profile.. along with how therapy utterly failed to solve the problem, hence the additional cheating.
You are right in your suspicions that this behavior develops unhealthy expectations regarding sex and marriage. Worse though, it normalizes pornography in such a way as to destroy emotional intimacy within the relationship (and thus ruins any chance at a satisfying sex life for either of you). The WS who gets involved in this kind of lifestyle believes that s/he is the normal one and the betrayed mate is just a prude.
Like you, I found the accounts and the emails, so yeah... it's devastating. But you know this is NOT your fault. Nothing you could do or not do, say or not say, can make another person betray their own values, and that's what this is all about really. It's about character. As you'll see in my profile, I bought into all the excuses, the "unmet needs" fallacy. We got into therapy and worked on the relationship, blah, blah, blah. Ten years later, he was back at it again, because....
MARRIAGES DON'T CHEAT. PEOPLE DO.
Inside your WH, just like mine was, is a man who only pays lip service to his personal code of ethics. His values of Fidelity and Honesty are infirm. There's nothing inside him which puts a full STOP to cheating and lying.
When he tells you that he wasn't getting a, b, or c from you at home, what he's telling you is not just that he feels like he DESERVES these things, but that his behavior is predicated upon yours.
He's not a man of his word. His espoused beliefs are of no more significance than his arbitrary whims.
Like you, we all beat ourselves up, giving at least some credence to the excuses we hear from our WS. It all sounds so plausible. Maybe s/he really did need more sex or more attention or more blah-blah? we torment ourselves. But I promise you, having been where you are and having bought into all the bullshit...
CHEATING IS ABOUT THE CHEATER.
Your WH needs to change. He needs to learn how to actually stand for the things he claims to stand for. If he wants to stand for pornography and hook-ups, he needs to be man enough to own it. If not, he needs to remediate his relationship with his own values system because...
WE PROTECT WHAT WE VALUE.
His words told you one thing, but you see that his actions speak the truth. If he valued his promises to you, his marriage, his family dynamic, his reputation, etc., his actions would reflect that. Right now, he values the addictive chemical rush he gets from his pursuit of pornography and sex. THAT is what he values.
The day after I broke into those accounts, I saw an attorney and when I called my fWH home from work, I told him I was divorcing him. We've only got one tool in our arsenal when it comes to demanding more from our mate, and that is our utter REFUSAL to accept less than what we deserve. I was unprepared for the onslaught of tears and snot-bubbled promises to change. I allowed my compassion and my desire to hold onto the status quo move me to accepting a form of therapy that doesn't even make sense when we examine it more closely. It took me nearly five years to recover from the same kind of betrayal you're describing now, and it wasn't really fixed so I just ended up going through that and worse a decade later.
This obsessive/compulsive interactive porn thing doesn't get better on its own. That's my experience and it's also my observation. There's a biochemical cocktail released within the body which pleasures the reward center of the brain and over time bigger risks are required for bigger rewards. It's a snowball rolling downhill and it doesn't stop until there's something INSIDE a WS which prioritizes better boundaries.
I'm sorry you needed to join this club no one wants to be a member of, but glad you found us.
It really does help to hear from people who understand.