I don't know anything about pot belly pigs but the American Guinea Hog is a small pig that is really good for meat. They stand about 30" tall and weigh much less than other larger breeds.
I think there are some other "small" breeds, not sure what is the smallest. I'm thinking that Pot Bellies may be the smallest domestic breed? But I don't know that for sure. I know we had some little pigs someone gave us, they were not Pot bellies, they were probably 40lbs, but I can't imagine that there would have been much meat on them. Their piglets weren't as friendly as the pot bellies either.
I've known people that have eaten them, but most have said they were not impressed! Actually someone just yesterday said they had eaten one, but I didn't ask them how it was.
And I'm not completely sure what is average, but of the ones I've known of I'd say around 5 piglets.