My thoughts on the moving off the X to the 6. You are on the same line as if you did not move at all when you are facing a gun. From my FOF if you do not move off line and just stand still you get shot either a fraction before you pull the trigger or fraction of second after you pull it. No matter how fast you are you can't out run that bullet. I see that as you both die. So movement off the X needs to make the BG change his aim point, the more you do that the better.
As to someone closing the distance on you such as a knife attack most people will move back to the 6 walking backwards I say you can't move backwards faster than someone running forwards without falling on your Bu**. My thoughts are that all movement needs to be with the feet pointed towards the way of movement. Hard to do and move straight back to your 6, can be done but harder than if you move at a angle. Specially for us older guys.