How does Nick feel about Tom and Daisy's marriage?

Nick believed their marriage to be a sham.... he felt that Daisy should have grabbed her daughter and run... not walk out the door.

It seemed to me that the thing for Daisy to do was to rush out of the house, child in arms — but apparently there were no such intentions in her head. As for Tom, the fact that he “had some woman in New York.” was really less surprising than that he had been depressed by a book.