Thanks, Ben ...
Interesting that your teaching duties interrupted you. My own work responsibilities interrupted my reading of your essay this morning (I'm traveling on business). Actually, I was re-reading since I read and rated your essay with a high score days ago. Still organizing my comments.
What is often called the "surprise version" of 20 questions (because the questioner is not aware until the end that there is no predetermined "right" answer) has the advantage of self-organizing its own constraints. Godel would say that those constraints were written in "The Book" even if one were incapable of calculating them. IOW, even given that not every infinite series has a finite answer, every answer requiring infinite time has a uniquely corresponding series of "questions." This stuff gets very abstract, and domain-dependent, as, e.g., Dedekind proves that there exists a pair of numbers in Dedekind cuts whose product is sqrt2, though one could never actually write those numbers.
The bottom line is that we really know very little about the continuum. Neither in terms of the number continuum, nor of spacetime.
What we *do* know, is that correspondence of boundary conditions to measurement values in any physical sense requires a bounded length of time. So a coordinate free measure of functions continuous from the initial condition is bounded in space and unbounded in time (and nevertheless consistent with the conventional general relativity interpretation of a universe bounded in time at the singularity and unbounded in space).
"Perhaps locality should be defined in terms of interaction: if two systems directly interact, they are considered local." Right on brother; that's the way Einstein saw it, too. Further, though, it is of deep consideration that Einstein noted " ... if two ideal clocks are going at the same rate at any time and at any place (being then in immediate proximity to each other), they will always go at the same rate, no matter where and when they are again compared with each other at one place." In other words, the clocks do not lose their local rate of change; no matter how spacelike separated, they are always timelike correlated -- which gets into your metric question. I won't try to answer it, because it's already been answered by Joy Christian's topological framework. Indeed, Joy obviates quantum entanglement, and takes full advantage of a topological idea of distance that ordinary geometry cannot accommodate.
Thanks for your thoughtful comments. I'll get around to commenting in your forum as soon as I can.
All best,
Tom