I've seen a few posts that ask what the difference between speed limit and speed limit with warning on the MFD. Basically it's trivial. If you set warning and you're on the Navigation linked section of the MFD and you have the compass and speed limit sign showing, and if you exceed the speed limit, a slight orange outline will display around the speed limit sign. That appears to be all it does. Pretty useless really, but there you have it.
Not much higher. I currently have just over 11K miles with just over 60 mpg average for the year, Here are the EPA estimates.