Welcome to the Pocketbook world.
1) Don't know, should work, is working with all my Pocketbook devices. If it is a firmware issue, contact them f.i. via
https://www.e-reader-forum.de/f/pocketbook.167/
2) SetUp your windows explorer to show hidden directories.
3) There might be a way via terminal (has to be installed on the PB) and bluetoothctl but it is quite complicated. Here is a tutorial for tricking the device into accepting a bluetooth keyboard:
https://wiki.archlinux.org/title/bluetooth_keyboard