It's loud enough, I can turn it up all the way on my macbook and it's not too loud. Oh gawd, the gore is grim (spaghetti, popcorn!) Balancing the volume of this audio with the audio in the movie would be good.. maybe you're going to combine them?
I see maybe abstract washy watercolor backgrounds in limited colors for sky and earth.. and simple tiny little bare trees and hills sprinkled in.. way far in the back..