That Is weird but i get the feeling that he may not fully understand it OR at the vary least he believes that Edith believes it and he always doubted her so now he will be on her side no matter what she says or believes.
Also F**k the author! she could have been seen as a sympathetic figure in when she first got sent to the world but as soon as she started to killing the Ediths she lost all sympathy....
The author replaced her and lived her story.
But once she married Cliff, the story reset and it started again and again until I think it drove her a little more crazy.
She tried to break the story herself at first, but gave up when it kept getting put back on the same path.
About then is when she started pulling other people in to be Edith.
I'm still curious how edith even became aware of the story, and even more curious how she was able to do that weird stuff, like bringing in others and such.