Answer: The Sevenths mans view changes as time goes on many times in the story. At first he beileved that K had smiled at him in between the first and second wave. Then he starts remembering it a little less and doesn't look down on it as hard when he moves away.
A - Not a knocker but Marley's face
This shows that the knocker transformed to the supernatural by becoming not what it was - but the face of his dead co-worker.
A1: every one except em.
A2: Greek is not a Celtic language.