Wow. The answer seems like it's good in the context of an affair, but not in the context of sexual addiction. For a sex addict, any kind of fantasizing requires caution, because it restimulates the habit. And I would go beyond "is it degrading"? If the fantasies are about your wife doing things she would never actually do, then you are just watching homemade porn and re-enforcing objectification of your wife instead of moving you toward a loving connection with a real human being. Please be very careful and honest in your assessment of what you are actually doing.