I'm going to focus on some shooting mechanics before I give my answers to your question about "
getting off the X".
You're really asking about three different problems:
1) Hitting a moving target while standing still,
2) Hitting a stationary target while moving, and
3) The combination of 1) and 2): Hitting a moving target while you are also moving
Note that these are not things that you are going to learn at an indoor range, shooting stationary targets. You're going to have to find a place where you can safely practice each one. As well, you're going to have to find a skilled buddy (or a team) with whom you can practice. But once learned, these skills are incredibly valuable.
Lessons I learned about hitting moving targets while standing still:
I learned to shoot a moving target by building a low, heavy cart, mounting a target stand on it, and then having a buddy pull the cart using a rope (sometimes using pulleys) while I shot at the target.
1) Using the cart to simulate a "Tueller Drill", I found that my ability to hit the target was better the further away the target was. The closer it came, the more I was simply point-shooting and the more quickly I had to move my gun. I found that I had a visceral desire to move off the line the closer the target got to my position. Lastly, there was no way that I could be aware of objects or persons in front of or behind the target as it got close to my position; and I was unwilling to fire at a close target that was about to pass by my side.
2) Shooting at a target moving right to left (or at oblique angles) is not too tough if the target's motion is predictable. If it is moving at more or less constant speed. And the target has some distance to travel. And if it moves in a straight line. But a target that starts/stops repeatedly, changes direction unpredictably, and moves quickly between close-by points of cover/concealment is very difficult to hit reliably.
3) Shooting at moving targets from more than a few steps away is especially difficult when using a handgun. Hitting moving targets from distance with a PCC, carbine, or shotgun (anything shoulder-mounted) is easier.
Lessons I learned about hitting stationary targets while moving:
1) Shooting while moving is best practiced using steel targets. The immediate feedback helps a lot.
2) I've only met one shooter who could reliably hit stationary targets at more than bad-breath distance while moving full speed. More can reliably hit stationary targets if they learn to take slow, steady steps (duck-walking?) that minimize movement of their upper bodies. Most shooters who are just learning to shoot while moving are in the "spray and pray" category. We have to learn to duck-walk before we try to run...
3)
Shooting while advancing is very different than
shooting while retreating which is very different than shooting while
moving laterally with the target off your left shoulder which is very different than
moving laterally with the target off your right shoulder. Moving laterally, you need to learn to walk forward and backward. You have to learn all of these.
4) Putting a couple of shots into a stationary target from the holster
at the beginning of a move to cover is pretty easily learned.
A funny observation: my wife and I were ballroom dancers in college. My body automatically shifted to dance footwork as I learned to shoot while moving. Viennese waltz was a close analog. In a Viennese, both dancers minimize up-and-down movement of their upper bodies and shoulders while they move rapidly, laterally, around the floor. I found that my body waltzed as my eyes and hands shot the pistol.
Lessons have I learned about hitting moving targets while moving:
This is tough. Very tough. The skills are athletic and highly perishable. This is why SWAT teams practice so much.
With that background, these are my answers to your question about moving off the X in a deadly force attack:
Learn to put one or two shots quickly into a stationary attacker while you are taking quick steps off-line. Don't move, and then stop to shoot. Instead, shoot WHILE moving. Once you start moving, don't stop. Run toward cover. Bob and weave, accelerate and decelerate, just like a running back. While moving at full speed, don't try to shoot. You'll likely miss.
Once you shoot at him, your attacker is likely to realize that he has another appointment somewhere far away. And will try to get there quickly. Remember that once your attacker is moving, he is unlikely to have the skills necessary to shoot you reliably. But he may still try to wing shots your way while he makes his escape. If he puts enough rounds down range and is "lucky", he may connect. But probabilities are against it.
If you are moving and your attacker is moving, neither is likely to connect with the other. Especially the further apart you are. Don't risk putting bullets into innocents downrange.
As far as drawing from the drop, I defer to
@.38 Special 's excellent answer: