I just own a Russian (non-WiFi) version of the Basic Lux (PB615) so can't answer all your questions.
1. Only books I've used (so far) on the 615 are ones I've side-loaded (DRM free).
2. The 615 does go into full sleep mode (it can be set up to 60 minutes before it does that). It takes about 12 seconds to come back to life. (This is on a slower CPU than the HD3 has. Also firmware 6.x is now available for the HD3, this may have changed from 5.x, I don't know. 5.x is also still available for the HD 3.)
EDIT: I like the idea of Adobe ADE built right on the device, it means you can borrow books from Overdrive directly and also buy Adobe DRM ePubs directly from bookstores, without having to have ADE on your computer.)
3. Don't use these. (Sorry)
4. Don't use it. (Sorry)
5. Don't know. It's very light (155 g) so that may be true.
6. Don't know for certain, but I'm pretty sure you're right.
7. No, not IR, multi-sensor capacitive touch. (Sorry.)
8. Yes, it supports sleep covers.
You can read in a full screen (no header or footer), it will load custom fonts and there are 24 graduations in font size.
Here's a link to the HD3's home page (PocketBook just recently changed their website)...
https://pocketbook.ch/en-ch/catalog/...ch-hd-3-copper
In addition to Tech Inn, you can buy the HD3 at Grooves.Land for U.S. delivery... (the price there includes shipping, but I think it's still bit more expensive)...
https://www.grooves-inc.com/pocketbo...er&utm_medium=
GoodEReader also sells PocketBooks in the U.S.
https://goodereader.com/blog/product/pocketbook-touch-3
I think this is the most expensive choice, however (when you add in the $20 shipping).
Good luck. I thinking of getting one of these, but first I need to sell off some of my other eReaders (if I ever get around to it).