I'm trying to get some sense from you OP about whether you still want some help. I'll presume that as you're updating, you do.
No your DD needs to stop looking through the laptop, but I absolutely understand why she did so. She is behaving like a lot of people do when they have suffered a betrayal and shattered assumptions about a loved one.
There is an urgent need to "make sense" of it and find the scale of the problem. This sort of "fact-finding" activity is a way of filling in the gaps and is common after a relationship shock of any kind. I'm more surprised that it wasn't you doing this instead however, but you haven't had much time since.
You need some calm time to discuss all this with your H and assess what this means. You're currently trying to fill in the gaps about your many unanswered questions and only he can answer those - and only you can decide whether you feel he's telling you the truth.
To all those posters defending porn and people's choice to either use it or work in the industry, the "choice" defence is utterly spurious. If users really think this is a defensible choice, then do it openly and not in secret - and have the balls to live with the consequences of that choice. Don't piss about with your partners' choices by keeping secrets.
And people who make an active (rather than a co-erced) choice to work in the porn industry need to consider how their choices harm women and the cause of equality generally. Not every "choice" is defensible politically and to see these kind of "choices" dressed up as some form of empowerment or evidence of liberation is nauseous.
Most of all though, have some bloody humanity for the OP. She is saying that she hates porn and has strong political views about it. Writing post after post telling her either directly or obliquely that she she is making a fuss over nothing and needs to get over herself, is arrogant and unhelpful.