Hypnosis

It's weird that no one has come up with the possibility that everything we see at the end is hypnosis. I have several arguments in favor of that theory:

1. The movie is playing with the audience in every possible way and trying to fool them. It quickly becomes obvious that the most obvious thing is a lie.
2. The whole crew is acting a bit suspiciously, conspiratorially in one way or another. There is a strong feeling that the only one who does not understand what is going on is the protagonist himself.
3. Before the scene with the appearance of the “devil” we see a hypnosis scene where we are literally explained that everything we see is a lie.
4. The “devil” starts killing everyone, but not the main character. A producer appears from somewhere and drags him backstage.
5. Whatever the devil is doing, it's hard to explain his appearance. Kill everyone?
6. In the final “dream” scenes we see hints that the main character is under hypnosis.