I don't think it is a crazy question at all because I have wondered the same thing! I finally did some research on it and came up with - you should weigh it after you cook it. This is from the Mayo Clinic-
"Weigh the meat after cooking and after removing bone, skin and excess fat. A 3-ounce portion of cooked meat is equal to about 4 ounces of raw meat. A 3-ounce portion of cooked meat is about the size of a deck of cards."
As for the batter mix question I think I can answer that too. Lets say you have a cake mix and it calls for oil, milk and eggs. You may add corn oil, full fat milk and eggs, while I might add applesauce, skim milk and egg beaters. There would be a big difference in calories, fat etc between the two. So they give you the unprepared nutritional amounts and you have to figure the rest for what you would add to the mix. Or use the prepared figures if you put in exactly what the recipe calls for.
On the popcorn they probably aren't adding in the fat it takes to cook the popcorn in because some people might cook it in oil and others might use a hot air popper.