He really needs to go back for a culture to figure out what the vet is dealing with. I would have to agree if you are not happy with the results of your current vet you need to move on and look for someone new. The poor little guy sounds like he is just miserable
Just a thought~when was his last dental? When I had Truman as a foster his ears looked much the way you are describing and he also had a very bad respiratory infection too. It all started with a horrible infection in his mouth that had spread to his ear canal and lungs. It almost sounds like he might have several different things going on with him. The infections too a very long time to clear and once he had his dental it never returned.