Diesel Engine Specific Aid

I recently purchased the Vacuum Troubleshooting kit and have begun to tackle some minor issues with my wagon.
Right off the bat I find something not specified in your manual.
I started with a vacuum pump test and my gauge is reading 16.5 inHG. When I remove the line from the booster it reads 19 inHG - neither seems REALLY low, but are below the 20-23 inch range.

I have two questions:

1. Is there a way to determine if my checkvalve is leaking versus a slow leak in the pump itself?

Lower coolant line leaking at the radiator. Got the two lines unscrewed at both ends and the clamp removed. Is it possible to remove these lines without lifting the left side of the engine and removing the motor mount?
If the mount must be unbolted, is it possible to remove just the screws that attach the motor mount arm to the engine and then just the motor up to slide the lines over the arm and under the engine?

Have a blown radiator which I pulled- How do I do an engine compression check to rule out cracked head or blown head gasket w/o the rad in place? Doesn't make sense to reinstall the radiator (-it's blown) or install a new rad just to test. Any ideas will be welcome as none of the mechanics down here seem to have any clue...

Driving down the interstate on my way to a gig (I'm a musician)- First noted the BATT light come on-Which I assumed correctly to be a shot belt- but also noted the engine was overheating.This is a new (3yrs old) OEM BEHR radiator I installed) Pulled over-antifreeze all over, radiator cap intact,but the top of the radiator was tilted about 20 degrees from horizontal, tilting up at the engine side, exposing the rubber tubular gasket around the top, and the metal mesh underneath. Obviously bent up somehow and in doing so disconnected the plastic housing.