I am sorry to hear about this horrible experience. My family's dog had a medical issue as well and we went to 2 different vets and both vets proved completely useless. We had wasted weeks of time that may or may not have saved his life. We eventually went to
Vancouver Animal Emergency Clinic and they had proved to be extremely helpful and informative.
If you are within the area, I suggest giving them a call and arrange a visit. I do hope that your Bischon gets his hearing back.