That is excellent FE for the KOH! And what a beauty too
Receiving two different averages for a morning and evening commute is not uncommon. Road elevation, harsher warm-up from overnight and in cooler temps and even traffic conditions so that is not really a big deal.
The SG-II however has a calibration routine built in that you perform at each fill. More --> fillup and input the gallons you filled from the pump.
WRT city and highway calibration, I am not exactly sure what you described. Can you reiterate?
Thanks and again, great car and offering great FE