Does Run Speed and Endurance affect the Mount as well or only running?

yes and yes. but ive found i only see returns at every 100 point mark. at 690 i notice no difference from 600. endurance kinda sucks as although you get the discount, sprint taks a flat % of your stamina so if you save 100 stamins, it still takes the same % of whats left essentially giving you a bit more on the top end but a faster drain on the lower end.

Thx