Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Chester has an upper respiratory infection that has led to wax in his ears and a fluid build up.
Respiratory infections lead to swelling of the lining of the the respiratory tract and inflammation, and that can cause a fluid build up in the inner ear. While that is uncomfortable and can cause a decrease in hearing acuity this fluid should dissipate as the respiratory infection and inflammation resolves. It may take several weeks for the fluid to completely clear after the inflammation is gone, but given time that should happen.
You can give him an amino acid supplement called L-lysine at a dose of 500mg orally twice daily. If the fluid is caused by inflammation from a Herpes respiratory infection this should help. This amino acid interferes with virus replication and will shorten the infection's duration and severity. Good supplements to try are made by the Viralys brand which comes in a powder to add to the food or a tasty gel.
If a secondary bacterial infection takes hold antibiotics can be useful, but if this is related to a viral infection then antibiotics aren't likely to help.
Certainly if he has an immunosuppressive virus like Feline Leukemia or Feline Immunodeficiency virus then those will allow the infection due to poor immune system function. Has he been tested for those viruses? If not he should be.
Maybe the fluid in Chester's ears isn't entirely due to a respiratory infection however. Sometimes we can see nasopharyngeal polyps form however, and those can cause fluid to accumulate in the ears too. If he doesn't have an immunosuppressive virus and the inflammation and fluid in his ears linger he should be sedated and your veterinarian can check him for polyps.
Best of luck with your fellow, please let me know if you have any further questions.