Backing up with any steerable front axle set-up takes a special skill because the front axle jack-knifes easily. Further, backing any short trailer is challenging and backing it with a long wheel base tow vehicle is even more so.
Dolly towing with the rear wheels on the dolly is risky at best and a really bad idea. None of the dolly manufacturers condone it, nor do the car companies approve. The caster set-up of the car's front wheel alignment puts tremendous stress on the steering when towed backwards at highway speed. Caster is what makes the wheels return to center when you turn a corner going forward, but the same effect tries to turn the front wheels 180 degrees when backing. That's not a concern at 1-2 mph, but looms large at 55-60 mph. There is more than a small chance that the steering wheel lock will break, or even the steering linkage itself. The towed vehicle will fishtail badly if the steer wheels are not locked.