In order:
As far as we can tell, Billy has a thing for children. It may be pedophilia, it may be Billy wants to be a child again (ask about the pink overalls outfit). He says it's because his comic is for preteens-teens, but his behavior tells a different story.
The art is like that because Billy sucks as an artist and makes no effort to improve. The comic is a vehicle for him to push a certain ideology, not a medium to entertain. The comic
used to be called "Assigned Male: the Adventures of Stephie (who happens to be trans)." It was misleading: you go into it expecting some Little Nemo surreal, or even something like
Craig of the Creek, but nope. From the first comic, it's Stephie howling about being trans.