My opinions on 1 and 4-
1- I have spent a great deal of time understanding and perfecting geometry on my setups (obssesive). on a set up like the elevator where the horn and servo arm swing in the same plane pushrod length has no effect on throw symmetry assuming the rest of the geometry is correct. on a perpindicular plane set up like the ailerons excessive angles from short pushrods should be avoided. a longer pushrod also affords less wasted force, less angle error and  generally speaking is easier to setup for throw symmetry (if thats what youre after). an extra couple of inches of carbon tube pushrod length adds a negligable amount of weight too. There are more important factors to linkage setup than pushrod length and a lot of "rules of thumb" that are just not true.
4- the rudder may require most of the servos capacity but the typical twin servo elevator or ailerons having low friction, with the typical throws and proper ratios will likely never need more than 1/4 of the servos capacity.