RE: Aiming at long distances
The distance the arrow travels is further than a straight-on shot, but the distance from point A to point B (base of tree to target) remains the same.
A exaggerated example is this--say you are 90 feet up at the target it one yd. from the tree. You won't shoot it like it's a 30 yd shot, although the arrow is traveling that far.
On a very long shot from a treestand, the angle and actual distance traveled might make more of a difference, but on your typical hunting shot just go with the distance from the base of the tree to the target.
Chad