Looking for some affirmation (8 3/4 rebuild not successful)

again your pattern looks very good --just get in there to set the preload on the pinion bearings correctly and you should be good --- if by checking the rolling resistance of the complete assembled differential you have only 20 in/lbs you should be more in the range of 50- 70 in/lbs as long as the pinion preload is right as well as carrier bearing preload.
the shim kit with the solid spacer gives you enough shims to set the preload correctly by adding or taking out shim in .002 increments -- itsa mix and match process and can be tedious . you should not have had to shave down the solid spacer for this to happen.---