That's a nice and big active area. I still don't understand how you will insulate your stator. Will you powder coat it or will you spray paint it with some plastic paints?
The spacer thickness of 0.8 mm is too much, IMO. If I were you, I would try 0.6 mm or 0.7 mm. You'll also need to increase your bias voltage higher.
For the metal itself, I was just going to leave it as is. I've not had a problem with exposed metal on the stators in my previous builds. If I have any issues, I suppose I'll spray paint the inner-face as I've done on some PCB stators. I don't anticipate any safety issues with sweat/dust screens and meshes on both sides of the driver.