It is possible that some of these symptoms may be related or they may be independent symptoms. There are individuals with immune system problems that are more prone to infections. The drainage is called vasomotor rhinitis and is probably not related to any of the other issues. It is also possible that you have a chronic sinus inflammation that gets recurrently infected. I would speak to your physician about all of these symptoms to see if a more in depth evaluation is needed.
Hey buddy, are your cough's productive? If so, you almost definitely need surgery. Had the same cough as you. I'm still having sinus infections, but not with the cough after surgery. Its almost definitely caused by nasal polyps that make the infections difficult to kill.