The stance is the 9 punches and boxing fundamentals. All of the defense courses cover head movement

The 9 punches and the guide to boxing fundamentals are very thorough in both of those concepts

The jab lands Simultaneously as the lead foot lands on the floor not the back foot. If you throw it when the back foot lands then you can’t throw the right hand going backwards without bringing the front foot back first which is a significant loss in time. Your footwork will always have a hitch.