Meniere's disease? Can't get ENT to take us seriously

We live in the Seattle area. My husband has been sick for a year now. He has constant ringing in his ears and a feeling of fullness. He also has terrible vertigo that happens for hours every day. He's seen three ENTs thus far. They've done an MRI and CT scan and have found nothing. They've put him on beta blockers and told him to eat less salt, but have done nothing else. Every new ENT is a 3 month wait - every time. Every scheduled lab is another month - every time. His family has a history of Meniere's disease. My husband is losing hope. He wakes up every morning wondering if life is still worth living. He told me the other day that he would understand if I wanted out of our marriage because being married to him must be dreadful at this point.

He's only 42. We have a 10 year old son and an 8 year old daughter. We are desperate. Does anyone know of ANYTHING that we can do to get a doctor to take my husband seriously? Should we give up hope?