Tough to say what happens while the ball is still in flight. I would guess that it's completely legal - it'd be no different if you broadsided a groundhog - you'd play your ball where it lay.

As for your friend in a tree - it's a 2 stroke penalty as your ball is moved by someone acting with your authority and on your behalf.

So then theoretically, if you could hit him in every tree, and he could make a perfect ****, you could get your round done scoring 3 on every hole.