Shedding "horrifically" tends to be par for the course with rabbits. They molt four times a year - two "light" molts and two "heavy" (where they shed and replace their *entire* coat).
As for the growth from his anus (especially since it seems to be getting worse), you should really take him to a rabbit-savvy vet to have it looked at.
It's abnormal to have a clump of poop stuck to a rabbit's bottom... is your rabbit overweight, arthritic and/or on a diet that allows him a lot of pellets? "Poopy butt" typically stems from one of those causes...