Unfortunately, there are other losses. The power purchased and the power the battery puts out are not the same, not to mention what makes it to the wheels. The EPA very clearly states that 59 to 61% of grid power makes it to the wheels.This calculation appears to be incorrect
I get a much higher mpg using your inputs:
1 US Gallon of diesel contains 40 kWh gross energy
40 kWh x 44% x 95% = 16.7 kWh net generator output
Teslas model 3 use about 30 kWh per 100 miles highway (less in city driving)
Therefore 16.7 / 0.3 = 57 mpg
Still pretty good.
We can easily power a vehicle with a 44% efficient diesel engine, or a 41% gasoline engine, almost (lock up converters/manual transmission) or even directly driving the wheels (accord hybrid clutch to axle setup) with variable drivetrain losses. It is hard to believe that it's better to use that same engine to run a generator, through a transformer, into the grid, transformed out of the grid, through a charger, into a battery, out of a battery, through a controller, into a motor and to the wheels? Especially when that battery also powers the heater, requires heating, and self depletes.