1) I think you've made this too complicated. All you need is two events, one for left and one for right. When Stapleton is overlapping the sprite on the left go to previous layout, when Stapleton is overlapping the sprite on the right go to next layout.
2) You set Stapleton position but you don't actually create the object. When you go to a new layout you need to create Stapleton unless it's in the layout view by default.
3) Again you don't have a cursor anywhere on the layout so it can't load it. If you look at Final Hall you'll notice that the cursor is off screen.
Some tips :
Previous/next layout works by using the order in which the layouts appear in the Project bar list. So next will always go to the next room if you list them in the correct order you want in the game.
When you go to a new layout it unloads everything from the previous layout in memory, and loads everything on the current layout. This is why it can't see your objects. You need to have them in the layout already or you can spawn the player on start of layout.