So of course I'm still jealous at your video camera...
When I look at your video (combined with the pirouettes), I wouldn't focus that much on movement for now, but more on relaxation. Because even though he has some very soft movements - the softness still seems to be mainly in the muscles and less so in the head.
I think that Special is an extremely sensitive horse, which is great for Haute Ecole training and playing with tiny cues, but the huge drawback of that is that those extremely sensitive horses are also very allergic to unwanted touches. And of course we call them 'cues', or even worse, 'aids' as our whip is supposed to 'help' te horse - but in reality it only helps us humans get what we want. It doesn't help the horse mentally or emotionally when coming to terms with an exercise, and that means that while we think we help the horse to understand faster what we want from him, with all our cues in fact we're putting him into a pressure cooker. And that often is not at all what the horse wants.
I love the fact that the leadrope is hanging through: he still managed to almost bump into it a few times, so I wouldn't shorten it, rather keep a better eye on your own position because that influences the length of the rope as well.
And I would ditch the whip - I'm sorry, but I can't make anything else of it.
When I see you, I see a lot of myself, and I was very whip-orientated as well - as soon as I had it in my hand, I automatically found a way how to use it to 'help' the horse. Leading to the pony's learning all their stuff as planned, but also responding to every touch with the whip with a nice swish of the tail, and I see the same in this video with special. You point/tap and the tail swishes. You take the whip away and stop and the tail is down again. That really is a message.
I tried to use the whip a bit less for a while, but that turned out to be a real struggle for me (being a true addict) - and then ditched it completely for about a year. And lo and behold: all our precious haute ecole exercises and collection disappeared!
Apparently our collection was almost entirely based on the fact that I was using unpleasant whip-cues to push them into it.
So we had some 'retraining' to do, but most of all some rethinking, and then our training became even more @liberty and our collection became based almost 100% on bodylanguage and mimicry. About a year later I slowly started holding a whip again
and not using it for touching but only for pointing, and by that time the unpleasant memory the pony's had of pointing whips had faded and they seemed to see it as just a stick/Tiger/part of my bodylanguage (for example when I ask them to turn the other way when lunging at liberty).
I don't know if it's possible for you in your training area, but because Special seems so sensitive I would actually love to see him at liberty, so that he has a chance to walk away as soon as it's too much for him - now he will always first has to refuse a request in order to get that point across.
That automatically leads to internal conflict/stress.
Don't get me wrong: I really admire everything you've achieved in such a short period of time, and you're the only one who knows both your horse and your own goals and how you want to achieve them, but I would see this point in your training as a very good example of what you two will be able to achieve (and even more than this I think!), and now let the exercise-thinking go for a while and focus on the emotions of the horse instead so that he will learn to play with his movements and discover that moving like this is actually fun - not even because of treats, but simply because moving like this together with you is fun. And as Special is such an elastic, energetic horse, I don't think it will take a lot of time for him to discover that either!
That to me really is the basis of the art of natural dressage at liberty; the fact that the horse enjoys playing with you and is enjoying every second of the training process, not just the final result when the teaching is done, the whip is gone and the 'aids' have become more subtle.