Sorry for my late answer, i'm a bit busy at the moment.
1. As inameiname wrote, you need to install PoP's merged-developer-keystore (link in 1. post) to play the kindlet as a "real" one
2. I don't understand the problem, the folder (\mnt\us\)developer\K3MusicManager\work\music should be created if you start the kindlet...
1. I also got this idea, but after some research to me it looks like amazon avoided this in their exaggerated security-limitations. Of course you can create KeyEvents but i found no way to send them "out of the kindlet" (i.e. java class Robot isn't compiled at the kindle and every try to bring it there manually failed until now).
2. Oh, i totally forgot about that, and hey, there we have a use for kite
3. To tell the truth, i was just lazy AND i didn't expect anyone to have such a great list of streams oO Thanks, i will use a few of them on my own
-swap pages with the physical buttons "next page" and "previous page"
-use Q-A-Z instead of 5-Way-Controller
-paging support for streams
-auto-mounting of /mnt/us/music/ to /mnt/us/developer/K3MusicManager/work/music/ via kite
-some other little bugfixes
To update, install the missing programs and replace the new files (as long as you replace the kindlet with the new one directly the mount issue won't take effect).