I have to agree with what just about everyone else has to say. Your poundage is plenty for ethical shots. The key, as you already said, is shot placement. More poundage can help you get through some bone if you hit some, but you never want to hit heavy bone no matter what you shoot.
as for tree stand shooting, it is always good to be practiced and sighted in for how you will be hunting. i personally have no impact difference when shooting from a stand or the ground, or anywhere in between. you will want to practice shooting in any situation you might hunt in, like practicing from a stand or in a blind, but you probably wont have to worry about your sight being off. but everyone has their own experience with their own shooting and set up, so its just something you need to practice and see if you find a difference shooting at different heights or on the ground. They advertise those fancy range finders to compensate for height differences, but that stuff isn't generally an issue for most bow hunting situations, unless you hunt around steep inclines like in the mountains.