What role does Walter Mitty's wife play in his fantasies

Walter Mitty's wife does not play any role in any of his fantasies. This is suggestive. Apparently his fantasies are, among other things, a means of escape from his hectoring wife. He has a "secret life" because his fantasies are kept a secret mainly from her. It is also suggestive that there is no apparent misogyny in his fantasies. If he hated his wife and wanted to get rid of her, these feelings might be detectable in his fantasies. But he seems to be dependent on her because he is absent-minded, incompetent and introverted. She takes care of all the practical matters of both their lives. He might be lost without her. He fantasizes about being a man of action, but he must know he really isn't. There is only one fantasy in which he appears to be fantasizing about being romantically involved with a another woman. That is the one in which he is testifying in a murder trial.

A woman’s scream rose above the bedlam and suddenly a lovely, dark-haired girl was in Walter Mitty’s arms. The District Attorney struck at her savagely. Without rising from his chair, Mitty let the man have it on the point of the chin. “You miserable cur!”  

Amusingly, the words "miserable cur" remind Mitty of one of the assignments his wife had given him when they parted.

“Puppy biscuit,” said Walter Mitty. He went into an A. & P., not the first one he came to but a smaller one farther up the street....“I want some biscuit for small, young dogs,” he said to the clerk. “Any special brand, sir?” The greatest pistol shot in the world thought a moment. “It says ‘Puppies Bark for It’ on the box,” said Walter Mitty.