The video does a somewhat decent job determining #1. Doesn't mention at all about determining #2.
"Pivot" could mean anything, right? If you drive a nail through your shaft 7" from the tip and turned the cue around that axis, you'd see that you'd start to miss the OB completely after the 3rd ball or so in your diagram. So, common sense says you're supposed to HIT the ball; therefore, you must always pivot in such a way where the arc of your pivot hits the "correct" center of the CB. This drives the pivot point farther back, depending on distance.
For instance, if a 90/90 shot was within a diamond in distance, most people retain their flat hip pivot and move their alignment to a ETC orientation. This doesn't have to be done--- you can recognize that the "shot circle" is smaller, thus having a curvier arc around its circumference. You can maintain the 90/90 alignment and pivot along this smaller circle and make a harder "turn" to center.
What does "arc" mean? And at what point do you shift from ETC to ETRE? How do you know?
See above. If you're still confused, pinch your cue at 5" from the tip and rotate around that point. Do the same for 7", 12" and 24" as well as from the buttcap. Pay close attention to the arc your tip makes as it makes its 1/2 ball turn. For all intensive purposes, when you pivot from your buttcap, you'll see that the tip takes a shorter (more direct path) from the beginning of your pivot to the end of your pivot (center ball).
If your tip follows the path of line 1 and line 2--- which path is longer? Therefore, the arc of your pivot has a profound affect in which "center" of the CB you land on. That's why when you say you missed 9/10 shots from a medium distance, you probably took no care in the world in your arc based on the distance (and/or alignment). Given, you probably followed the directions you had at the time-- but there's obviously more to it than that.
Perception errors, in my opinion, account for a huge percentage of misses as well. People THINK they're aligned ETE, but they're really not. Their tip is pointing out to left or right field when they think their alignment is good.
A great way to overcome perception errors for ETE alignments is to pretend you're shooting a stop shot. A stop shot is typically an alignment an intermediate and above player can SEE and repeat as often as necessary. Once you're standing up behind the shot (let's say this is a 90-90 to the left) and you're pretty much in position to step into the shot as if it were a stop shot, move your feet 1" to the left of where you normally would step in. Instead of aligning your cue to the center, align it parallel to the left at the left edge and then hip-pivot to center ball. If you do this correctly, you should feel "uncomfy" pre-pivot and then pivot into comfort. Otherwise, if you step into shot with your body in a post-pivot position and pivot to center ball, you're pivoting from solid comfort into an unstable body position. It's just the opposite when going to the right.
ETC alignments can present perception errors for players with a strong dominant eye (such as myself). You'll probably find that one cut direction is far better than the other. I recommend you always start from a center-to-center position while standing up (since we all know how to SEE a stop shot) and rotate around the OB from one ETE to the other edge and find the midpoint. Over a few months, you'll find that you can do this with an amazing tolerance. Developing this ability to "see" lines and alignments usually isn't an overnight thing; however, it'll take players WAY less time to train themselves how to see these positions versus the base of a ghost ball.
Anyways, hope this is helpful. I'm jacked up on Dunkin' Donuts coffee at work and was energized to make a good reply.
Dave
