backing is a breeze for me except one part.....

Look for marks on the ground you can line up with for testing.

 

The school will penalize you for actually bumping the dock? That makes about as much sense as a screen door on a battleship...

 

I just whip out the working part of my anatomy and Mark the ground. Since you’ll be doing the same in a peelot soon enough it’s totally ok. The tester will give you bonus points for marking your starting point and then marking where you need to back to. I also signed my name and made a little picture of a truck for a double bonus.

 

I think the testing procedure is very odd (a "slight" bump of a dock is standard procedure to me). In this case, I'd step off the distance from the rear wheel to the bumper, and then go to the "dock" and step off the same distance, and put down a glove or something where the rear trailer wheel has to be.

 

I’ve got the same depth perception problem last few years. Seems to be age related. Could be worse if it were the other way around, backing into everything. I’ll walk off the distance behind my trailer, then do the same using the step as a reference point and something on the ground. This testing seems impractical, bumping a dock nice and easy, then a little push to make sure you’re up against it is the Professional way.