If they were fatty and tough I think they needed more time in the cooker. The fat should render away when they're done. Before they're done, the meat will pull back on the bones but the bend test will tell you when they're done.
If you haven't eaten all of them yet, stick them in the oven at 275° until they pass the bend test and report back.
Sorry to hear they did not come out how you wanted but it is a learning process. As far as temperature goes, you cannot go by an absolute temperature because the same temperature on various cookers will produce different results. You need to learn how your equipment works. Based on what you told us, I would shoot for 250° on the next cook. And stick with the same kind of meat until you nail it (probably on your next cook.)