Why did Mr. Scratch want the signal at the observatory, in alan wake Amercian Nightmare?

I'm a little confused about the observatory part of Alan Wake's American Nightmare.

Dr. Rachel Meadows says that Mr. Scratch came to the observatory because he was interested in the strange signal. She managed to isolate the signal. Scratch then forced her out of the control booth and tried to make sense of it himself, but apparently couldn't understand it. He became angry and sabotaged the imaging array.

Later, Alan repairs the imaging array, and Rachel is able to produce a printout of the signal. Alan recognizes that the signal contains a road map connected to the new reality he is trying to create, which leads him to the Drive-In Theater.

So, what I'm trying to understand is:

1. How did Mr. Scratch know about the signal in the first place, and why did he want it?

2. Why couldn't Scratch understand the signal when he looked at it? Was it simply because Rachel hadn't gotten a good enough fix on the signal yet?

3. Why is Alan able to recognize the printout as a road map? Does he remember enough of the story he wrote to recognize what the signal represents?

4. Most importantly, did Alan actually write this whole sequence of events into his story? For example, did he write that Scratch would go after the signal, fail to understand it, sabotage the observatory, and leave Rachel alive so that she could later help Alan retrieve the signal?

5. If so, is the signal itself essentially information Alan arranged to send to himself as part of the story/escape plan, knowing that his memory might become unreliable after crossing over from the Dark Place?

I'm trying to understand the in-universe logic rather than just why these events happen for gameplay purposes. If there are manuscript pages or dialogue that explain this, I'd really appreciate the references.