That sounds rough OP. I think the possible computer issue needs to separate from the porn. If mine had gone around my parent blocks, particularly the router settings, they would be in serious trouble. That puts their younger siblings at risk. Their curiosity doesn't give them extra privileges. But, the punishment for that needs to be another thing.
With my oldest at 13, it was admitting to adult-rated comics on his phone followed a few months after that to my needing to fix his phone and finding he never closed any of his windows in his browser...just kept opening more...and the very embarrassing thing while we both sat there while I closed through several deviant art pictures. All drawings and nothing that explicit but yeah.
First time, after a very long talk with us going through all the comics and discussing the issues, he did lose his phone for a bit as he had broken the rules and he lost the comic app when it was given back.
Second time, more conversation where on one hand we did discuss that his action were typical and how we and many people we knew had looked at similar at his age, we also discussed the limits of what we would consider fine and what would be punished (like altering parental blocks, showing it to others, and so on) and showed him how easily we could tell if he breaks our trust on this.
We also discussed porn and the issues mostly mentioned in this thread of it being unrealistic, being unable to be sure if the people involved consent, that a lot of it involves violence against women, how orgasms are pretty much the brain's ultimate encouragment tool so it's important while his sexuality is developing not to have that associated with such images as well as the addictive and drive for more hardcore that porn can have particularly as my son has addiction in a lot of his family tree so I'm very upfront that he is at higher risk of that than most just as I am.
I was upfront that I would rather not explain all the issues as he's only 13 but that if he did break my trust and chose to watch porn, I would likely find out and I have a growing reading list of books by more eloquent women who've also lived through it so if he chooses to, I would ensure he was well informed on his choice. Not exactly gun blazing or nuclear but I think it certainly made it less appealing.
As someone who survived sexual exploitation as a teen, and some people I knew then did not, I have no patience that while it might not be every single woman, the pain of poor, scared, often drugged up women that the porn industry relies on and most sites, including porn hub, take footage from each other and have absolutely no checks whatsoever if the women are paid (or keep their pay, a lot goes to 'facilitators' of various types and pay is often used to push women into certain acts) or cared for and the US industry - which is the majority of pornhub content - has fought hard to keep age and welfare checks out.
People can insult my intelligence all they want, I was a dumb messed up kid, it's better than saying I enjoyed what I've done to survive.