Thanks so much for your insight! Here's what I ended up doing to fix the first few items, in case this helps anyone else in the future:
- For the black-background setting, I ended up using Kindle Comic Converter. Target device set to "Other," margins set to "black," and custom width/height set to PW5's resolution. Works perfectly!
- Frenzie, thanks for directing me to where the page-turn-direction setting lives. I ended up assigning a gesture to toggle this. I suppose it doesn't really matter when manga turns LTR, especially since I'm not viewing anything in 2-pg-spread mode, but I do like to keep to the original "feel" of things.
- Gave up on trying to connect to OneDrive -- found a better way to wirelessly connect to my Calibre library (which was what I was trying to do), but using the OPDS catalog feature. And it's MUCH easier to navigate than my OneDrive Calibre library would have been.
- NiLuJe, thanks for the gesture tip! I decided to just use gestures rather than profiles for this -- made one gesture to set Night Mode + brightness 8 + warmth 85%, and another gesture to turn Night Mode off + brightness 18 + warmth 70%. Works perfect!
And I'll be very excited to see the page turn animation feature in a later update.
Thanks so much!!