1. I've never once had a waiter ask "one bill or separate?" The waiter just brings the bill. What the hell kind of vibe did the waiter pick up from this couple that made him think that maybe they were going Dutch Treat?
2. So the question causes the male on the date to panic. Why? What was the conversation about all dinner? Was it about Toxic Masculinity? I mean, what could possibly have been the topic of discussion to make this poor shlub react in such a way to a simple (though perplexing in that it comes from the waiter) question?
3. Poor shlub reacts to the question- and his panic- by jamming a piece of gum in his mouth, to buy time I guess. Yeah, sorry, buddy, but you've already blown it. At this point you might as well say "separate checks, please" because you aren't seeing this particular girl again, ever. Nobody is desperate enough to come back from more of this nonsense.
Learn your lesson, buddy. Guys pay. Just pick up the check, and if your date objects, apologize and agree to separate bills- but try to pick up the check first. This isn't rocket science. Oh, and save the gum- despite your actions on this night, you aren't twelve years old. You shouldn't be worrying about your mom smelling alcohol on your breath. Grow up. And better luck next time.