Precisely. Butt is a bit of a mis-nomer as the cut of meat actually does come from the shoulder. They sell them boneless also but I prefer them bone in as it makes a perfect natural thermometer. When the bone slides out nice and easy with no meat attached..... it is done!
Like most everyone said it sounds like you have a butt there planet. As far as a rub jeff's I hear is really good I have found a store bought thats really good to me. It's Old Bay the seafood seasonings but it for meat. There's a whole section here about rubs and sauces on the front page.