For font info, see
Format conversion and fonts. Some fonts don't work, and it isn't always clear why. Your desktop PC probably has plenty of .ttf fonts on it already. Not all can legally be transfered to another device though. The thread
Which font do you use? has some recent suggestions.
It does sound like DRMed MOBI has been removed. One way to tell is OK -> 6 Settings -> 4 About. If you have MOBI DRM support there should be a 10 character "MobiPocket PID" at the bottom of the page. You need this PID to authorize DRMed MOBI ebooks (including lending library ebooks). The same PID should show up if you connect to a Windows PC via USB and open Windows MobiPocket Reader.
You can download other firmware versions. For a list, of sites see
EZReader Firmware.