Without going to to enormous detail, I have a 6 yr old Yellow Male who is very stinky. A strong yeasty, almost obnoxious odor. The vet's have tried various and sundry forms of antibiotics and other meds to no avail.
Doesn't the "great Dane Lady" have a special diet for dogs who may have yeast throughout their body? Google "great Dane Lady" and you will get her website and it goes into major detail. Certainly may help your boy if you have tried everything else.
If you've eliminated all possible causes and the odor still persists I would try giving him chloroplyl capsules daily. They are completely harmless and should help reduce the odor. Worth a try if all else fails.