Will having the blade .004 above the outfeed table have a measurable
affect?

I've been told .002" However, a better test is to take a flat stick, maybe 1"
square, 12" long, and mark two lines in tthe middle, 1/8" apart (be accurate).

Place the right hand line on the outfeed table, and then manually turn the
cutter head. The stick should only move to the second line. You have to check
at both ends, plus once at every jack screw.