How is your general health? I had actually seen two cases with patients having general health problems and infection never got under control until they found out the medical problem. If an endodontist gave his expert opinion that the root canal looks fine and the infection according to surgeon might be coming from the same tooth...In my opinion it might be a good idea to have a physical done with immunity check.
You may want to see your primary care physician to rule out any systemic problems that are undiagnosed. The symptoms you are describing could be tooth related but with your dentist, an oral surgeon, ENT and endodontist all evaluating you thoroughly, it sounds unlikely that its a localized tooth problem.