Yes, his stinky breath is probably from his teeth. You can try brushing/cleaning/scraping them yourself, but at this point, whatever you get off probably isn't going to make much difference. The cost varies widely depending on location and whether or not he needs extractions. I am guessing in rural Fla you would be on the lower end, but don't really know. I understand the reluctance to put him under, but there may be more going on than just tartar build up, an abscess, gum disease, a bad tooth. All of these things will ultimately affect his overall health, and he will feel so much better afterwards!
So yes, a vet visit would be the first step, good luck.