OH-My-Gosh! My husband has this same smell from his teeth. I have never discribed it this way but that is exactly what it smells like. Unbareble at times. Can't be too mean to him becuase I have my own pit odor issues that for some strange reason finally went away since moving back to the states.
Here is his history incase you have something in common. He had a protective sealant put on his teeth 15 years ago. He has never had a cavity in his life and he is over 40. He had an apendisitis and lympnodes removed. He has a lot of moles. He can smell up the bathroom and his smell, smells old and musty. Like mold in an old basement. Hope this helps.