I can answer this question-------"How far does the roosting bar need to be from the wall?" (cause I did it wrong the first time)
See my BYC page for pics of my Coop, you can see the ladder style roost I made that pivots up to allow me to shovel out the deep litter compost results once a year. When I first built it, the roosting bars went all the way up the ladder to within a foot of the back wall.---------------------I quickly learned that chickens like to poop while roosting, the deep litter works for that, the back wall didn't. Well, I suppose it did work, just not very eye appealing to see the multi-colored streaks running down the wall. So I removed the top roost bar and now the closest bar is about 18 inches from the wall.