I am sorry to hear you are worried about Little Bit. I am a veterinarian and will do my best to help.
The bad odor is from the bacteria infecting his bad teeth. Having the bad teeth cleaned, and pulled if they are too far gone to save, is the best way to get rid of the odor.
When I see dogs with this problem, that can't have the dental work done because of health, age, or financial reasons, I do try a course of antibiotics to treat the bacteria and infection. The smell will come back when the antibiotics are stopped, but we sometimes do "pulse therapy", or using antibiotics intermittently, as needed.
There are products that contain parsely, charcoal, and other odor absorbing ingredients that you could try from your vet office or pet store or online. These come as sprays, water additives, and dental treats.
Let me know what else I can help with or answer. Rebecca