Well, we've had yet another long conversation (who could've guessed? lol). So as it stands, the new final verdict is that he is going to try his best to compose himself, and to remain faithful. Unbeknownst to him, however, I have slightly eased up on my own mindset. After careful consideration, I have decided that I am fully prepared for the time when he DOES slip up. Now I know that I will still be angry with him for a bit, and I know there will be complications. But I also know that we'll be able to work through it.
And I was wondering: you know how there is the concept of "a mulligan" or otherwise a "freebie" in most monogamous relationships? Well, maybe there could be a way to possibly amplify that concept, in a possibly freer way. As in "you get X amount of freebies". Not saying this to him, of course, but maybe as a mental checklist?