Bad breath is a symptom of lactose intolerance. Unfortunately, lactose intolerance can affect people in different ways so that makes it sometimes for doctors to diagnose, especially with your other medical conditions. Here is some information that I found that perhaps you can share with your husband and doctor. Also, that fact that not eating dairy improves the situation proves that it was part of the problem.

The bad breath is much more
than "morning breath".

It is powerfully strong and people can sense it from feet away.  Others may think the person has poor oral hygiene when in reality they are lactose intolerant.  The oral hygiene has nothing to do with their bad breath.   The bad breath is caused by the lactose rich foods sitting in the person's   intestines and fermenting.  The body tries to get rid of the gases that are produced as the result of fermentation by having them reabsorbed by the bloodstream and exhaled out.

The hydrogen breath test is a common way doctors make the diagnosis of lactose intolerance.  This tests measures the amount of hydrogen in the breath.   Normally, very little hydrogen is in the breath.  But undigested lactose in the colon (large intestine) is fermented by bacteria, and various gases including hydrogen is produced.  The hydrogen is absorbed by the intestines, carried through the bloodstream to the lungs, and exhaled.  In the test, the patient drinks a lactose-loaded beverage, and the breath is analyzed at regular intervals.  Raised levels of hydrogen in the breath indicate improper digestion of lactose.  Certain foods, medications, and cigarettes can affect the test's accuracy and should be avoided before taking the test.  This test is available for children and adults.

Source: http://ibscrohns.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=ibscrohns&zu=http%3A%2F%2Fwww.families-first.com%2 Fhb%2Flactose.htm

Hope this helps!