The piece is coming along nicely. In watching how you play, i.e., your technique, I noticed that you are playing with your wrists at a slope downward from the keyboard (some like this, some don't, I play that way after trying other ways...), your elbows are out quite a bit from your sides (David Saperton and his students play that way; I did for years until Peter Feuchtwanger changed things for what was for me, the better), and (I believe because you are sitting a bit high) Your back is inclined towards the keyboard. In short what I see is a mix of different approaches which work for the most part but not for everything which may be why you are having some of the issues with control that mention.
From where I have sat and sit, you could go two differing ways.
Go full on Saperton - sit a bit higher, keep your wrists above the keyboard or level to them on downbeats, keep your hand curved "around the ball" as he said.
Go towards Horowitz and Feuchtwanger - as PF did with me the first time I played in his master class before letting me start to play(!), try lowering your bench at least an inch and move back from the keyboard as well. Release your hold on the palm ball and play with flattened fingers, curving just the first joint.
Your call, but it might be worth the experiment. Talk to iternabe and look at what he's done using the PF approach and how it's freed him, but, as I said, it's not like Saperton and his most famous students (Bolet, Foster, Simon, Cherkassky, Masselos) and his less famous students (like yours truly) can't play well and be relaxed.
Basic posture and position are the foundation for everything else. A focus area for later exploration is wrist rotation with the Taubman folks doing it one way, and PF telling me in a public session, "I don't use the wrist that way; do it like this". Details another time. Clearly both approaches work.
Hope this is helpful to you and others.