That is very detailed analysis and lots of insights, Michelle. Great work!
With cylinder, you can usually get away with less in close-up than distance. Successfully reducing from the first (already lower cylinder) in differentials is usually indication that some cylinder reduction in normalized is also possible. It is all very much a personal experiment to be sure, and you want minimal directional blur. More of it present in less ideal lighting conditions!
20/30 seems ok for normalized, though careful about having that being because of directional blur. All you really want is a little bit of challenge at a distance you use a fair bit, for active focus.
If you have specific diopter thoughts based on this, feel free to share for review.