It’s always seemed to me that the subjective perceptions of time by any organism present far easier challenges than the fundamental issue of time on a physical level. The “arrow of time problem” is clearly a tangible phenomenon regardless of how our brains, or the central nervous systems or autonomic signalling systems of any other living creatures happen to react to it in order to cope with the real world. As you correctly say early in your article, the two options appear to be (i) spacetime as a permanent meta-construct though which we for reasons not yet understood move rather like a bug crawling along a length of ribbon, or (ii) a perpetual “now” in which only our records (neural traces, writings, pictures, etc.) indicate that the “now” of a few moments ago occurred and a totally unknown future “now” that will occur after this one has instantly passed. One big question for quantum mechanics is whether space and time are infinitely smooth “all the way down” or whether there are ultimately discrete quanta of spacetime along the lines of the Planck constant. It’s plausible to imagine that once we’ve answered this question we’ll be in a better position to understand more about the nature of spacetime at the meta-scale.