Luke counts one to seven because there are seven members of the family, there's also seven steps from his bed to Nell's bed. You can see that near the end of the episode, when he awakes because Nell is awake too.
After Young Luke is spooked by the talking tube, he runs down the main staircase and two ghosts can be seen standing in the doorway to the right of the stairs.
At around the 8:40 mark, a ghost can be seen standing on the right side of the screen. (The previous shot of the window lingered a little longer, highlighting that the ghost was not there previously.)
In the kitchen, when Luke and Nell are examining the tube, a white face can be seen through the glass sliding door on the left.
When young Luke is checking the talking tube in the upstairs room, a reflected face can be seen on the right side of the tube.