You're playing with the classic "heel up" method. Your heel is up the entire time, and the weight of your leg keeps the beater more or less "buried" against the head when you do isolated single strokes. Like nearly all drummers, you let the beater rebound instantly off the head when doing a very fast series of notes (such as when you were doing the repeated double strokes). This is pretty much what everyone does since there's literally no time to keep the beater pinned to the head when you're playing a very fast series.
For your double strokes, you're using a technique that I teach called "toe/ball." The first note is made with the front of the toe, and the second note is made with the ball of the foot. Nice.
You've also intuitively figured out that moving far down the pedal can help for very fast playing because you get a lot of pedal movement from very little foot movement. The pedal does require more force to push when you're that low, but that's a tradeoff which is often not a problem. You seem to be doing just fine with it.
The one bit of constructive criticism I would offer involves your isolated single strokes. Whenever you played an isolated single, you tended to get one primary note followed by numerous little extra hits and buzzes. I see this even from very famous drummers, and it has always been a pet peeve of mine. When we hit a tom, we don't make one note followed by 2 or 3 quiet little extra hits. I suppose some people probably do, but for the most part, that would be very obvious as poor technique. And yet...nearly everyone does this and accepts it as normal when playing the bass drum. A famous studio drummer told me that a microphone CAN and WILL pick up on that, creating a muddy sound. So, if you truly want to bury the beater against the head, do so with more conviction to avoid those tiny residual taps. Or better yet, treat your isolated single strokes just like all of your other notes and let the beater rebound clear away. There are ways to achieve this.
It was fun analyzing your video. I hope you found this helpful. Extremely nice job with your drumming. That's some pretty burning bass drum playing!