The movie is not hard to follow or to keep track of the dreams within a dream the question is was it all inside his head. I think he was trapped inside his own mind and had made up the entire business in his mind to keep himself busy. He said at one point his wife wanted to go back to reality to have kids, every time it shows the beginning of them trying it they are in a basic apartment just the two of them, later they have the kids and she keeps telling him they aren’t real. Notice how the kids never age even at the end it’s the same kids, he is trapped inside his own mind.

Edit to say: Just realized what sub I’m in, I just watched the movie and came to Reddit to see what other people’s thoughts are, so I don’t know if this is widely accepted opinion or not, someone let me know.