Hi rahrah300 -- it sounds like this situation has been really confusing for you. Having your trust broken is very difficult and it can throw us for a loop to say the very least. Now, I may be totally off the mark here, but... reading that you posted in a few different places and also talked to friends is making me wonder if you are trying to ask others how you should feel. I want to emphasize that - though it's totally fine to sort out your feelings with someone or ask for advice - ultimately
you will know what's best for you here. I bring this up only because I have the tendency to seek a lot of input from others in situations like this, and only recently have I realized that it can disconnect me from what I want because I feel pressure to do what others think I should. I do not know if this is case for you, but for me it was because for a long time I believed everyone just somehow knew better than I did. Just in case you needed to hear this the way I needed to hear it -
you can trust yourself. <3
Back to your question -- no, I don't think having porn is an explicit red flag for potential cheating. I think it's possible to love someone and enjoy sex with them and also have a private sexual life that may not be as focused on them. It's hard to say what would be a red flag; relationships and boundaries come in all shapes and sizes, and something that may be a point of tension in one may not be in another. It sounds like you and your boyfriend had a really good and productive conversation: you shared your feelings, your boyfriend explained his feelings and apologized, and you've communicated what you're not okay with. It sounds like he was very receptive to your feelings as well. I think continuing to listen to each other and being forthcoming with your feelings will keep this in green flag territory.
Be a Blabbermouth! is a great resource for having potentially hard or anxiety-inducing conversations. Though it's more focused on talking about sex with a partner, I think a lot of those tips can be applied to a lot of different conversations.
I was also wondering about how you found the stash of porn. It looks like you said you were logged into his drive and looked through the files, found it, and then went through the folder. This may be a hard question to answer, but how were you feeling when you did this? What made you want to look through his files?