Hi Ivan. I suggest doing that same drill you did, but throw your sidekick waist high. This is partially a tactical point but also applies to the technique side of things as you're throwing the kick higher than your current flexibility allows. From a self defense standpoint, you don't want to be throwing head high anyway. Sure, it can be done if flexibility allows, but it's not practical in the grand scheme of things.
You have to pay attention to the pivot of your base foot, it needs to pivot on the ball only. The video shows that your feet really don't want to pivot that way yet, but you have to make them.
The questions you posed -
- How far back (towards the root leg) should one lean back whilst doing a sidekick, and am I leaning too far back?
There's one way to find out. Train the kick against active resistance, waist high. If you're leaning too far back you'll get the immediate feedback telling you so, because you'll go down on your butt.
After analysing a couple of videos I filmed previously whilst practicing, I saw I would sometimes skip the chambering and just execute the kick. I feel like this is faster, but would you recommend I include the chamber as I have attempted to do so in The video?
Pretty much the same answer as the first question. Practice it against resistant partners in your dojo.
You can either do it with them helping you, or do it without them knowing what you're trying to accomplish - by doing it while sparring against them. Cock it and lock it and dare them to come in. And keep throwing it, over and over, every single time they rush, even when
you have better options. It's a great way to practice a stop hit. You'll get hit or run over sometimes, sure, but that's how you put that kick under a microscope.
That particular kick, when thrown waist/body/rib high, is what's called a stop hit in general. (It intercepts an incoming target) and a Defensive Sidekick in particular.
Once you get it down, let me know and I'll give you a great two man shield drill that will drastically change your ability to hit with that kick against active resistance.