There are some little secrets on sanctuary, like between maps under that bridge are grenades, also in demo, plus in demo there are more grenade types...
What item button do you mean?
Anyway Doom cannot have floor over floor so I decided for that secret in there (unless done on some sourceport, but I made the map under vanilla doom through wadauthor), originally there is some ammo under the stairs, well it is not supposed to be exact remake or something.
And yeah I know that about the monsters, but this is doom afterall.
Also the exit in the secret area behind start is temporary one, exit is not supposed to be there, I had it there earlier so that you can exit the level, when I made only first two rooms. It is gonna stay there until I create a real exit I think.