For the first question I have no answer, because I don't have a 912, for question 2: Are you sure you made the changes for the correct reading app? there should be three choices, "Global action", "PDF / DJVU" and "EPUB / FB2". If you have assured this I'd try a factory reset or a new flash of firmware.
The last question needs a little bit more information. What screen do you get and what are the settings you made? In "settings -> appearance" you can define which scren you'll get as a shutdown screen, and in"settings -> clock" you can define times when the device will lock (not standby, power consumption basically the same as switched on) or shutdown (really off). Some time ago a member of this forum found out that power consumption for switching off / on equals power for round half an hour of use, so a setting for auto shutdown after 30 minutes makes sense.