Those sound like pretty good instructions to me, but for a first time visitor to Tokyo station, 15 minutes for this transfer is DEFINITELY tight. You will have to be at the exit of the train as it pulls into to Tokyo station and keep moving to give yourself a bit of slack just in case you take a wrong turn somewhere along the way.

It's definitely three escalators up to the main train floor and I am pretty sure that the third bank of escalators will always be to your left because you might have to make a 180 after the second bank depending on which ones you took up.

Another reason to avoid the elevator is that it usually takes a while to find, but if you do happen to see the elevator right in front of you as you get off the train, it replaces only the first two escalators. Take the elevator to the top level, turn left on exit, and follow the instructions above starting with #7 in that case.

I see no way you can guarantee you will even have the 15 minute transfer time if you are arriving on an international flight, as there is no way to gauge in advance how long it will take you to get through immigration -- it can take up to an hour although I think it has improved somewhat lately.