Very good points. I had considered a few alternatives, perhaps I should use (regularized) rshares, as I originally was considering, since those2 represent the relative rewards a post gets compared to all of the others for that 24 (I guess 12 now) hour period, if I understand it correctly.
On your second point, empirically the formula I use seems to give very reasonable values for two cases: 1) accounts like mine, which have a very small number of popular posts, and a medium number of not-popular posts. 2) accounts with a large number of popular posts, but also a large number of posts. As I continue to try other cases, they seem to form a reasonable spectrum, but I'm open to tweaking it if a better metric is suggested.
To your original point, I'll need to go forward with acquiring the measure for all users before I can regularize it. Alternatively, I'll need a good way of figuring out the total-payout at an arbitrary time-point. I haven't figured out how to get anything more complicated than the agreed-upon past 30-day SBD values.