I'm going to try to summarize what I think are key points and what I have understood about the game, sorry if I sound "strange", my English is basic-medium level, for some things I use a translator.
Door is the father of the saga, it is too implicit in the game, both by Door himself and by the Andersons. But the interesting thing is not that he is the father, what you have to ask yourself is... What or who is Door? It is clear that he is not human; In one manuscript he is practically described as a deity, something "more powerful" than Thor and Odin (who are two seers or paracapacited).
Between Control (in this game Dylan is talking about Door) and AW2, it can be understood that he is some kind of supernatural entity that has the ability to be in "all worlds at once." Probably the point here is that the Dark Place is a kind of place that "connects" parallel dimensions.
In Control, Dylan Faden says that "he was in the dark place and met a man named Door", Door can go to parallel dimensions and it seems that unlike the other characters, only one version of Door exists.
The concept of the multiverse is strongly implied here. For example, with Tom Zane there could be strong references to the Poet and the Filmmaker being fictional, but at the same time being real. In Control, Dylan says that in his dream "he saw a writer writing about a cop, but in another world, that cop was real." Do not confuse the Dark Place's ability to modify reality with creating characters: the game makes it clear that the Dark Place CANNOT create people or things from nothing. What Dylan probably means is that in one dimension, Alan Wake writes about a fictional cop, but in another dimension, that cop is real (could be a reference to Max Payne).
I mention Tom because I think he is the best example of this: in the first game "Tom the Filmmaker" does not exist. Not even Sarah Breaker knows him, he is a kind of urban legend. In the first game, Tom was a poet who had a similar story to Alan and ended up trapped in the dark place after trying to eliminate the darkness, also erasing him from existence. "Tom Zane the poet/diver" ceased to exist.
In the second game, the game's story seems to have been rewritten. We are told that Tom Zane was a filmmaker and the poet was just a role in his movie. But now Tom Zane was someone very famous and well known in Bright Falls, he had his own building, a commune of artists (almost referring to the sect) but some bases remain: his wife Barbara Jagger and he locked her up of him in the Dark place. Personally, I think Alan/Scratch or even the Dark Place is playing with multiple realities. There are some references to Tom the Poet existing:
Cynthia Weaver in one of the letters says that "she doesn't know why he is now a Filmmaker to everyone when Zane was a poet."
Jesse Faden in Control, in a recording with his psychiatrist, recites a poem by Thomas Zane. The psychiatrist accuses him of making it up, because there is no poet named Thomas Zane, but there was a filmmaker with that name in the 70s. Jesse is confused. It must be taken into account that Jesse is paracapacited and is also protected by the entity Polaris; probably, like Saga and the Andersons, she is not affected by the rewritings of history, which should be remembered that they affect the past as well.
Although less relevant, we also have the nursing home, supposedly built by Thomas Zane, one of the elderly people (Norman) says in a conversation between several characters that "he has been in Bright Falls all his life and did not remember this place." It could be another strong reference to someone rewriting history and influencing the past. We've already seen that the Dark Place can do it: it completely changes Saga's life and Logan's destiny.
I think that although it seems very complex, it really is not: Tom the poet probably existed in that dimension. In another Tom was a filmmaker and the poet/diver was a role he played.
Making an analogy, it is as Dylan says: in one world (alternate dimension/parallel universe) there is a police officer, and in another a writer writes about that police officer. I think the same thing happens with Tom. The filmmaker Tom is surely a product of the multiverse, a different version of Thomas Zane. What I can't explain is why another version of Tom has appeared: it may be the work/whim of the dark place itself, which we have already seen can open doors to other universes, or it may even be that Wake was interested in having a Tom Filmmaker (after all, a poet and a writer are essentially the same type of artist) to create a film and create an overlay to escape. Wake himself may have altered history; but I don't think he can "create" a Tom the Filmmaker, I think he has simply "lured" into the dark place a version of Thomas Zane in which he was a filmmaker.
A similar case would be Alex Casey. He is not Alan's creation, but the story created by Alan draws him to Bright Fall. Again, they make it clear to us that the dark place cannot create people. These have to exist. You can manipulate them and "use" them in your story, as if they were puppets, but you cannot invent a character. With Tom the Filmmaker I think it's the same: that Tom exists. In another universe, the Tom that existed was the interpretation of him (the events of Alan Wake 1). And I think that in this game, his story has been rewritten to conform this reality to that of Tom Zane the Filmmaker.
We could talk about how everything points to Tom being the origin, but he couldn't create Alan Wake either. I think this game is "playing" chicken and egg, but I think we'll have more answers about this in the expansions. We know the dark place can't create people, but Wake and Zane are identical. They're probably the same person, maybe in alternate universes where they've been using each other.
With Alan Wake I think something similar is going to happen; I think that in the game's universe, he is a real person, but in another, he could be a creation of Doctor Darling (Control character who also appears here) and the version of Thomas Zane the Filmmaker. I don't think it's a coincidence that Wake looks like Tom and has the voice of Darling, and that these characters seem to have some kind of escape plan. There are multiple references that Tom could be playing with Wake (before getting shot in the head he switches places with Wake several times, and Wake seemed quite disoriented as to what was happening, not to mention that the shot seems not to be affect you at all).
In short, in this game there is not only the fact that the dark place can alter reality. The multiversal concept is also very implicit, in addition to time travel. Time travel isn't exactly time travel, but we see references to it: when Saga summons Wake at the end of the game, it actually affected the past (when Wake came out near the beginning of the game), and we also know that the place dark can alter reality in the past (death of Logan), we also see that Wake, after leaving the dark place, interacted from within the dark place a version of Wake from the past with a Saga "from the future".
UNMARKED SPOILERS IN THIS THREAD 
