For the MaxLite fixtures:
1) yes, a single 1/2" knockout on each of the sides/ends.
2) doesn't say specifically, but you might want to read this: http://www.jade1.com/jadecc/courses/UNIVERSAL/NEC05.php?imDif=133. To me it sounds like #3 would apply.
3) yes, the knockouts line up, but I don't...