Ugh. I've been through the same thing with a friend who goes to Disneyworld several times a year. I mean, how many times can I look at a picture of her with Mickey and say "Oh, wow! How cool!" Some people seem to forget that no one else finds their vacation pics nearly as fascinating as they do. Add to that, my friend is operating under the delusion that she is a world class photographer and that each pic she takes is a work of art...yawnfest...!
Eventually I ended my friendship with her so I don't have that problem anymore (that wasn't the reason, of course). That doesn't help you much though, does it?
Perhaps you could say something gently like, "Friend, I know you've put them up on Facebook, so I'll look at them when I get a free minute" and then beandip. Then be true to your word-take about 5 minutes and skim through them. That way if there is a truly remarkable pic you can make a point of mentioning it to him. Regardless, at least if he asks you again you can honestly tell him that you did, indeed, look at his pics. You aren't required to study each and every one after all!
I would draw the line at allowing him to hijack me into looking at them at dinner, like you described. I would firmly tell him, "Friend, I will look at your pics online later, but I am hungry now so please put that away and let's order. You can tell me about your trip while we eat."
He can be "adamant" all he wants, but good manners does not require that you let him bulldoze you into spending a ton of time looking at, as you said, essentially the same vacation over and over again.
Oh, and if he ever does catch on that you are skimming through the photos, there's nothing wrong with saying (with a smile), "Oh, friend. I've been there, remember? And I've looked at 20 years of your photos from that place, too. I'm just glad you had such a good time!"