My 2 cents:
1 and 2. This cheese requires eye formation. This is very difficult, or impossible, to do with anythign less than a 10# wheel (about 12 gallons). I personally wouldn't even bother trying to make the 4# gallon version. The results will be edible, but just will not have the beautiful eye formation and supple texture fo the real thing.
4. Blue cheese yes, as you are innoculating for the ripening culture not starter culture. This method will not work for starter cultures, reliably anyway, but especially for long aged cheeses like a cheddar. If you get cheddar from Neil's you are better off eating it.