It is more to do with stance width, but trying to see where your feet line up with your knees when naturally jumping helps when you start to set up your stance. Its not scientific, you just have to gauge where they are. You don't really have to jump off a chair to see that when you stand with a good solid stance your feet wont face forward, they will be pointing out! Jumping off a chair just helps you understand your bodies own mechanics.
Binding angles are something you have to experiment with. I start beginners off at either 12deg or 15 deg (equal duck) whichever feels most comfortable.
i had one older gentlemen who had ridden before, insist i set him up with his back foot at 0 unfortunately he wasn't able to move on as easily as the others in the group, and looking at his riding i put it down to his angles, but he insisted on keeping it the same way.
Ultimately, if you are comfortable, there is no wrong way! If you get from the top to the bottom, and have the best time ever, who cares how you ride!!!
I just figure if you are like me, any advantage is a good thing, and I've seen countless happy faces at the end of a weeks instruction because they learned a new skill and actually understood how they actually got their board to do what they wanted... safely!