Get a second opinion. And I would definitely push for a bloodtest first. Doctors like to jump to the expensive procedures despite how unnecessary they may be. Try to find a doctor who has a side specialty in your husband's health problems. My doctor has a degree in psychology especially surrounding sleeping disorders. That isnt going to be helpful to you, but it is for my husband who has a sleeping disorder. Every doctor has their special interests despite that they are general practicioners. Also ask around. People you meet or friends may know of a doctor who has helped someone in a similar situation as your husband. It cuts out a lot of time spent finding a good doctor.
Good luck, I wish the best for you and your husband.