Very interesting stuff. And I'm glad to hear that the print was in very good condition. I've seen a couple repertory prints that have been quite beat up, especially at reel changes (presumably due to the reels having been plattered and de-plattered multiple times?)

And as to how dark the first Batman was, I have a theory. It had to have been dark enough that the Joker reveal actually worked. In every video transfer of the film, when he's standing in the shadows talking to Grissom, you can make out his face (to differing degrees depending on which transfer). But I just can't believe that Burton would have intended this; the original prints had to have had blacks sufficiently deep so as to almost completely hide him in darkness until he steps out into the light and says "You can call me...JOKER!"

(I have the same belief about Beauty and the Beast - there is no way in hell we were meant to be able to make out anything but a vague shape of the Beast recoiling into the shadows in the prologue. The West Wing scenes had to have had deeper shadows than any of the modern transfers - even in the brightened VHS/LD master, you couldn't make out his features very well, and I want to believe that was the intent.)