I appreciate your detailed intro, and can relate to everything you've written. I caught your post pretty much as soon as you posted it, and after listening, my first thought was, "Yep. That's Haydn, alright!"
I just listened again, and it's fun to listen to, and, yes, you are getting it to shape up nicely!
Since you seem to be pretty self-aware as to those things you want to fix, I will provide just one insight for you, regarding this:
[...] I don't know what happens when there's an audience, even when that audience is simply a camera, but so be it. [...]
It's called "divided attention," and can get you every time (if you let it!). If I can trust what I've read about how "multi-tasking" works, the summary is that the brain can really only handle one thing at a time. When "multi-tasking," the brain is chopping up attention to focus on 1) this thing, and then, 2) that thing, and then 1) this thing, again, and then, 2) that thing, again... and so on. The brain works fast, so it can *seem* like you're doing two things at once, but really you are doing one thing at a time, back and forth, really fast. You can see what happens when you try to do three or four things "at once." (My sister has a joke that goes, "Yeah, I have A.D.D. I get a lot of things done every day, but I never get anything completed!"
). Anyway, you can figure that when you are simply playing a piece and trying to follow the score and bring forth the music using all of your sensitivity and skill, you are already doing about a million things! (Well, o.k., maybe twenty-five.) Add an audience or a recording device to the mix, and, well, where is your attention, now? Furthermore, I suspect that the adrenaline rush happens because the brain is calling for a chemical boost to try to take care of all of the demands that the spirit and soul are putting on it in order to perform. So then, comfort goes right out the window, too.
My best playing (if I can say that) comes when I pay attention to the sound of the hammer hitting the string. When I put ALL of my attention right there, it seems to funnel the "sensitivity and skill" part to the right place. In fact, I have recently found "the zone" several times when playing for audiences. I actually chose to ignore the audience, and I was so focused on the sound that was coming from the piano that I became very, very calm. One of these audiences was a lunch-time crowd, and it was very interesting to note how many times during the hour or so I was playing, how quiet the room became as people were drawn in to listen. That kind of thing does not always happen when one is sending fluffy atmosphere music into the room for people to talk over. (That's why I'm noting that experience here for you. It was one of those significant leaps in awareness for me on a number of levels!
Adrenaline was not an issue, because I did not overload my brain. I think so, anyway. I was very, very calm, and the piano itself was a joy to listen to, so I just went with it!)
So, the "practice" is in focusing your attention on the right thing. Ignoring the recording device does take practice.
Just like learning to relax your arm to accomplish that one trill in that one measure when you get there, takes practice. For a while, I practiced with my recording set up in position all the time, just so I could get used to ignoring it!
Hope this helps! I'm looking forward to hearing the whole piece when you are ready to share it!