denverh
1) Correct
2) Correct
3) To my knowledge, there is no risk to brick reader with such script with CFWs that I know (mine, boroda's or amutin's) since the script does not get executed, if reader is connected to USB during startup. That allows you to recover from errors.
Note, however, that there seems to be a hard limit on number of items you can "mount --bind", it seems for x50 it is 3. After that it simply doesn't work. PRS+ is using 2 out of the box, 3rd if you use custom values in "LRF Text Scale".
Now regarding your custom CSS. Shortest way to create such CSS is to take
FontsAsInLRF.css and replace the paths to the font files.
You need to mention "font-weight:" when defining font-face only if there are different files for different font weights. I'm not sure if URL must be in quotes or is it optional.
And one important point: if you are using 2.0.11b, there is a bug with the path to CSS files. (will be fixed soon in 2.0.12b) As a workaround you put save your CSS file as /epub/userStyle.css in internal memory.