"There seems to be an anomaly with your numbers: The 100 kWh battery delivers about 400 miles of
range. How is it possible to go that far on the equivalent of 2.1 gallons of Av Gas?"

Eric- the main reason that the numbers seem skewed is the relative efficiency difference between modern brushless electric motors (often over 90%) and typical Internal combustion engines, which barely reach 30% efficiency.

For a reasonable overview of the gas vs. electric debate, I highly recommend an article in the January 2021 issue of "AOPA PIlot" magazine entitled "hp versus kW" by Peter Rez, "an Arizona State University physics professor from Scottsdale who flies a Mooney."