Edwin,
The idea is that time is an effect. How do we experience it? Our lives exist as series of perceptual impressions and so it's natural to think in terms of the narrative effect. So what would a point in time be? It wouldn't be an event, as they require some duration of activity to exist, be perceived and processed into a conceptual impression. This duration is a unit of time, like a second, minute, etc. A point in time would be the hypothetical division between one unit and the next. The assumption is it is dimensionless, but this is mathematically flawed, because anything multiplied by zero, is zero, so any point, spatial or temporal, cannot be dimensionless, or it doesn't exist. There would be nothing to divide one unit from the next. It is though, a handy concept and useful modeling tool, but that doesn't mean a dimensionless point can be real. So if you think about it from that perspective, the real question might be to ask why anyone would think "now" could even be a dimensionless point.
Consider that in terms knowing the position of a particle: Can a particle even be said to have an exact position, if there is no such thing as a dimensionless point in time? It would require isolating the actual object from any motion it might exhibit, should it even exist independent of motion. Think quantum string without the vibrations. We don't even know they exist, except as an explanation for the vibrations. Could it be there is no there there though? We think the noun must precede the verb, but does function follow form? Possibly one motion is simply matched by its opposite. The fact is that the more we explore the evidence, it seems this is the case, though we reject it instinctively. The search for the God Particle continues.
From the perspective of physical reality, there is just a bunch of energy bouncing around. To this energy, there is no time. No beginnings or endings. Events require some frame, or perspective, to be anything other than random activity. The pulsing of activity which brings together form and tears it apart always exists in larger networks of activity. These forms have a beginning and end, these are the units of time, whether lives of beings or the celestial cycles we call days. As they go from potential to actual to residual, the future becomes past. We think of this historical record as constantly increasing, but the reality is this information evaporates, as the energy manifesting it cycles through other forms. So there is no more direction than a hamster running in its wheel. Of course that same activity which destroys, also creates, so we can't have our cake and eat it too.
As for energy of that expansion, for there to be a flat space, where expansion is balanced by contraction, as is observed, it would seem that what falls into gravity wells is distributed back out across the space between them.
When Einstein first understood gravity to be contracting the measure of space, he added the cosmological constant to balance it out. While much is made of the fact that Big Bang theorists predicted the existence of background radiation, it should be also noted they seriously missed explaining how flat it is, as well as explaining the curvature of the redshift. Rather than reexamine the theory, two major patches, inflation and dark energy, were added. As you say, " if you or I were off by that much, we would be expected to recalculate everything that depended on" Big Bang theory.
Now Einstein himself proposed that for the universe to be balanced, there had to be an effect known as the Cosmological Constant. Every successive measure of redshift since 1998 has more accurately shown this redshift to equal what Einstein predicted, rather than that predicted by BBT. It is generally accepted that the space we observe is flat, that expansion and gravity balance out. That means there is no observed overall expansion, only expansion between the gravity wells. So why is it that we have both theory and observation that support a balanced universe, yet there isn't even a suggestion of discussion about the possibility?
We keep building ever more powerful telescopes and as far as they can see there are mature galaxies and galaxy structures and the only response seems to be; My, they grew up fast! Yes, they say those most distant galaxies only show the light of the lightest elements, so they must be young, but given the distance, wouldn't any light from heavier elements have been completely shifted off into black body radiation? Which is what we see a preponderance of, from the edges of the visible universe, but that's supposed to be the afterglow of the Big Bang.
Now that have built this theory of the entire universe as a single entity, going from its birth to its death, we can't help but suppose there are other such entities out there. What if the space we exist in is simply infinite and we are constrained by the horizon line of how far light travels before it falls completely off the visible spectrum? Do we really understand the properties of light well enough to insist this redshift could only be due to recessional velocity? The theory is that space itself expands and that is why we appear to be at the center, but if it was an optical effect, due to distance, the result would be the same appearance. When gravity wells bend light, such that the source appears to move, we know it is only the path of the light being bent. Wouldn't it be simple enough to consider a similar effect causes the other galaxies to appear to recede, as opposed to assuming they must actually recede? We only have a few decades of observation to go on.
If space itself were to expand, why wouldn't the speed of light increase proportionally, since it is our most elementary ruler of galactic space? What would determine C otherwise?The Doppler effect, as it is properly understood, isn't due to the expansion of the frame, but movement within the frame.
I better leave it at this, for the moment.