I really would not worry about the material on your grate bolts. You would be cremating your meat before they got hot enough to cause any problems. They will get coated in creosote anyway. You will never see them again if you put acorn nuts on them.
I prefer a smoke stack to prevent water from running into the it during a rain. Unlike a domed Weber lid - the entire lid of a barrel is lipped to collect water. That said, the flat lid will help keep your sauce warm.
Do care about what your nipples are made of - They will rust and make it impossible to remove the caps. Unless you are religious with oiling them - just use brass.
As for cleaning - use an ash pan. It is practically eliminates cleaning the bottom of the uds.