You can't make full even revolutions with a bar and watch it that it is making 12 or whatever inch lbs all the way thru, you are checking a rotational pre-load which a beam isn't designed for, you can with a beam wrench make a somewhat pull and guess it's the same all the way thru, however a beam to be accurate in what is is for needs the same hold at the handle all the time, which is why its designed for tightening a bolt and not a revolving load where the pull at the handle position changes. It's not the tool to use for pre-load, thats why a torque meter exists.
Checking pre-load isn't pull and see what it moves at, it is the entire revolution in one even motion at the same amount of force or speed. Making a complete revolution with a beam using the same force and holding the handle the same is not happening all the way thru a complete revolution or two
I've been able to make full revolutions on the axles I've done and the reading stayed consistent all the way around...
While it may not be the "perfect tool" for the job, it works just fine in my experience. Setting up gears isn't rocket science. Heck, many people set the preload by feel.
Anyways were starting to get off topic here. The OP can make his own desicion on whether or not he wants to pull the diff apart, install a new crush sleeve and reset preload once he looks at the FSM or another resource to learn what will need to do.