i have a similar problem and a partial solution;
I have a alpine head unit as well (x100 i think) which only works as far as i can tell in the ipoo OF. However as most people on rockbox.org, i cant stand it so i need rockbox on it as well.
I wiped the ipod (had to use itunes+ updater

), i then used mediamonkey to put all my music on. after that i put rockbox on it. after initializing the database, the tags are working properly and i can use my rockpod in my car as well. the only problem that I've found is that because of the stupid way ipod organize their music, all of the album art is wrong.
can anyone think of a possible way around this?
Thanks,
-Tom