no expert on castles either except from rpgs and movies, but I'd expect the gatehouse winches to be located in the house directly over the gate itself and not to the side as to get a vertical pull without the chains having to go over wheels and thus make it harder to lift. I'd also expect the gathouse floor to be twice the height of the portucilis so they would get pulled up in the walls below the gatehouse.
I see the idea of having a cut-off of floors accesisble from the battle - however if the battle will only take place in the courtyard it self, I'd keep the roofs. However if part of the battle is securing the gatehouse, you have to have a room with a winch to fight in, and of course a way to get up there .. stairs, ladders. Looking good so far though