Start by not snooping anymore.
This is a mess. You don't really trust him (hence the snooping). He isn't necessarily perfectly trustworthy or at least is diminishing your concerns (hence he claims it's been 'years' since a hookup with a guy yet the video is dated much more recently than that).
Plus you now have long distance going on - a killer for a lot of relationships, even more stable ones than yours seems to be.
So, what to do?
How about talking to an impartial professional, either together or separately? Get some tools for how to deal with this, and what to say, and where to go from here. Regardless of his interests in other people or other kinds of sexuality, the bottom line is that you need for him to be faithful (unless you want an open relationship, which I am taking that you don't, from your post) regardless of the wedding tackle being sported by the people in the porn videos he watches.