Thanks for your query, I have gone through your query.
The bad breath or halitosis can be because of the gum infection or food lodgement, since you are telling your oral hygiene is good, the other possible causes of halitosis can be because of respiratory tract infection or gastro intestinal disorders. Nothing to be panic, consult a pulmonologist and gastroenterologist and get it evaluated. Mean while, you can use mouth wash containing chlorhexidine.
you might be having a gastresophageal reflux disease, so consult a gastroenterologist.
I hope my answer will help you, take care.

Hello,
Your husband most likely has some periodontal disease. Gingivitis includes inflamed gums. Flossing is important to remove debris and particles from in between the teeth. Your husband should be up-to-date on regular dental visits which should include a professional cleaning. He should practice good daily hygiene which includes brushing, flossing and rinsing. Your dentist will determine if additional periodontal treatment is necessary.
Your dentist will also evaluate your husbands bite. This can affect how your husband is able to chew his food. An overall evaluation will determine if teeth are missing or additional dental procedures are needed to help chewing.
Acid reflux disease can cause some of the symptoms described for your husband. Does your husband have a coating on his tongue? Daily care should include brushing the tongue. A coating on the tongue can often reflect digestive issues. Hey high acid content is stressful to the oral tissues. Plan a visit to your regular physician to help control any digestive issues. Make sure your husband follows a proper diet and takes medication as directed to help control this.
Thank you for your inquiry. I hope you find my suggestions helpful.