Unlikely to really, it takes a certain amount of power just to achieve a given speed. Cars already have very low Cds and EVs are heavy so rolling resistance is high. Crash safety requirements and tech. also keep making cars heavier.
In very small amount and largely trial capacity. Look at test figures from magazines for kWh/100km not brochures. 20.3kWh/100km (AMuS test) for a Model 3 is about right yes. So it's over the top end of their estimate.
All you need is a bunch of solutions that your reference study suggests to be implemented nationwide, which would take forever and the scheduling, so as not to disrupt the economy would be a nightmare. This is a 30 year project minimum, probably more like 50.
If you want to ruin the remaining countryside. Better to wait for fusion power, distributed gen brings its own problems to the grid.