1 ) Yes, I'm on a Mac. Should have mentioned it
Now I remember reading about it once. I found an app that removes hidden files and eject the card/device in one go:
http://www.macupdate.com/info.php/id/27416/hidden-cleaner
And some help: https://www.mobileread.com/forums/showthread.php?t=33625
2) + 3) Not sure what I am doing wrong, but selecting my own fonts doesn't seem to be working. What I thought was working for MOBI, was just that the default font was serif and RTF displays in sans serif.
I've added a folder called 'fonts' at the root of the SD card and added font files (as per instruction on the Jinke site - adding the full family etc.) I'm also able to change font in the settings on the device, but the changes isn't reflected when I open a RTF file (I've tried several files and from different sources).
For now, I'm content with the standard display of mobi files, so I don't feel a great need to fix this at the moment - though of course it's nice to find out
why. I have been thinking about trying OpenInkpot - sounds as if RTF is displayed beteher there than on the standard firmware.
4) I downloaded Jan. firmware form Jinke - it might have helped. It actually did display the contents of the SD card - except it apparently couldn't detect any content. After experimenting a bit, I can see that if I take out the card when the reader is turned on, and
add files, and then put it back, the reader stays in display SD card content mode, but displays an empty list. This happened 2 times in 10 and not at all when I either deleted files or changed nothing. I think I can live with it
I'll remember the tip about hiding folders.