Just guessing here, but with the 2011-13's there is actually a key hole behind the push start button, maybe we would actually have to use the key inside the fob to manually shut the engine off. Completely guessing though.
'12 manual also says to hold down the button over 6 mph and eventually it will turn off. Doesn't help if it rolls off while tripping you in a parking lot Guess that just leaves the parking brake in an emergency.
Sure you will. Unless you kill the engine and put it in neutral. The power steering is belt driven and if the trans is still in "D" then the torque converter is still spinning as is the crank which drives the accessory belt. Since the engine is turning there is still vacuum. Things may be a little different than usual but it is not a complete loss.
Of course, if the car is rolling > 15mph then the wheel is pretty easy to turn. A number of cars run pumps that shut off power steering at speed anyway. Also, there is usually enough vacuum left in a system to provide for a decent stop even if the engine is not turning.
Actually IIRC the 2014s have an electric power steering pump so windmilling the engine will not keep you in power steering....