Serious infections can be helped by an operation (sorry, don't know the name of it) which cleans around the inner ear and removes any bacteria. But, in saying this, this operation costs around 1500euro and can have side effects including face paralysis.
I would strongly recommend bringing your dog to the vet, if you already have not, to get him checked out.
I also found this website while I was researching the topic for a project for school and I found it helpful so I hope it can help you!
http:/www.natural-pet-care.com/natural-pet-health-blog/dogs-puppies/what-is-an-ear-canker-in-dogs