Hey, Jonathan
Nice quality video, with clear articulation of your ideas.
Even though the video was primarily about "wrist rotation," you referred multiple times to the fulcrum while emphasizing the importance of it and demonstrating your approach to it.
Since you directly asked us for feedback, I think it's worth mentioning...
In terms of the fulcrum, there is another option as well...and that is to shift the stick so that it sits in the middle knuckle rather than the knuckle furthest from the hand.
It's really just a shift of half a centimeter or so, but it can make a world of difference for 2 reasons:
1) The index finger now becomes capable of propelling the stick instead of just creating the fulcrum.
2) The little segment of finger that is closest to the hand (technically called the "proximal phalange") now sits directly on top of the stick. This effortlessly stops the stick from getting out of position.
When we choose to do a little pinching fulcrum in the knuckle furthest from the hand, we pit our finger strength against the upward force of the stick. The harder we strike the drum, the harder we need to squeeze in order to prevent the stick from slipping up out of the fulcrum. It's a losing battle for most drummers, unless they play very delicate music.
I only mention all of this because you specifically stated that your students often have a "weakness in the fulcrum." In my opinion, that "weakness" is almost guaranteed if the student is trying to use the little pinchy fulcrum in the knuckle furthest from the hand while playing loudly. Again, the harder the student hits, the harder they will need to squeeze just to keep that kind of fulcrum intact. At some point, the muscle strength in the hand will simply give out...or the student will injure themselves trying to keep it together.
For better or worse, I know firsthand what I'm talking about here. I stressed and strained my hands to the point of injury years ago by trying to play loudly with that kind of fulcrum. Fortunately, Jim Chapin got a hold of me and knocked some sense into me before my drumming career was ruined. He actually had me release the index finger altogether.
Some years after that, I eventually reintegrated the index finger...but this time using the fulcrum in the middle knuckle. To give credit where it's due, I learned this approach primarily from 2 gentlemen already referenced in this thread: Bill Bachman and Gordy Knudtson. Both are wonderful drummers, wonderful teachers, and long-time friends of mine.
If you decide to try out what I'm suggesting, I think you'll find a dramatically increased sense of relaxation. It'll almost feel loose and out of control at first, but then you'll regain the control minus the need to squeeze harder and harder when striking the drum harder and harder. And as a bonus, your students will no longer have "weakness in the fulcrum" because the mass of the proximal phalange will do most of the work just by sitting on top of the stick.
I hope this input is helpful. Keep up the good work with the videos.