With reference to that curling little finger: Horowitz' did the same thing and it didn't seem to slow him down any! (as you may know, he also recorded "your" Scarlatti sonata).Also, for what it's worth, I tend to think that tension
First of all, I'm glad someone's playing an acoustic piano. There are so many videos here of digital performances. Not that I'm against them or anything, I have one, too. But the sound and satisfaction of playing a regular piano is no comparison. Even yours which isn't the best, I admit, has much more timbre, if you get what I mean. And in this scarlatti, it's particularly adapt.
If it doesn't ache or get sore, then good, I'm maybe a little over conscious at the moment as I've been getting some wrist pain and been heavily investigating piano technique and physiology. In some cases different physical aspects can compensate for what could be considered as bad technique that could provide an impression of good. Pain is really what it comes down to so if you feel none and play as lovely as you do, by all means disregard my comment. I better get uploading.