in game prefab editor zombie spawns + rotation

[White Warrior]

Hey guys, I've been making a castle as a prefab, but I'd like to be a zombie castle. Which mean that I would like to face a zombie army when getting in. In my prefab, there are rougly 400 sleepers in there, but of course they don't spawn in my world. is there a way to change the spawning file or another file to have all sleepers I placed to be in there? oh and another thing is I can't seem to rotate my castle the way I want. It's facing north but I place it at the northern top of the snow biome so I'd like to place it facing south