Thoroughly Confused

[Zampano]

Just got finished reading the book. I would like to note that I haven't seen the movie. The reveal near the last third of this book has me confused. I have a few questions with this reveal in mind:

1. Does the narrator need to be sleeping to become Tyler? I understand that when he is sleeping, Tyler takes over, but when he sees Tyler, is he also sleeping?

2. Assuming he was fighting himself in the parking lot during the first fight club, why did none of the onlookers point out to him that he was doing this. Seems the twist would be revealed much too soon if this were portrayed realistically. I understand this is satire, so the unrealistic reaction may have something to do with the satirical nature of the book.

3. How exactly did the aftermath of the condo bombing work? He goes to his condo to find it blown up, and then calls Tyler, but it is never pointed out that he is sleeping. When exactly did he fall asleep?

4. Finally, how does the ending work? Why did Tyler disappear once Marla came to the top of the Parker Morris Building?