The reason sodium nitrates and nitrites are added to meats like ham, bacon, and sausages was to inhibit the growth of the organism that creates botulism toxin. It thrives in an anaerobic environment, but is destroyed by heat. if the temperature is above 40', but below 140, and is a low or no-oxygen kind of place, then the organism can thrive, and release its deadly toxins into your food. But it also needs moisture.
That's why canned goods are heated under pressure, to reach higher temperatures that will destroy the critter before the can, or jar is sealed. The same is true with meats, including smoked bacon. The pink salt makes the environment inhospitable for the little nasty critter, as does an acidic environment.
Ever notice the pink color of bologna, mortadella, most dried-cured sausages, that's caused by the the sodium nitrates, and nitrites in the meat. Without them, smoked or unsmoked, they could not be dry-cured. They would have to be cooked.
You could salt-cure your pork belly before smoking it, but then you would have smoked salt pork, and that would be a whole different thing.
There should be some good guidelines on line, like this one: Maple-Bourbon Smoked Pork Belly | she cooks...he cleans
All of the recipes I looked at say to smoke or cook the meat at temperatures between 220 to 240 degrees, for 2 to 4 hours. There are a bunch of online recipes. Just google "smoked pork bellies".
Seeeeeya; Chief Longwind of the North
Hope this helps.