Seems like you've answered your own question, unless I'm misunderstanding you.
Set the group for /fat32-1, /fat32-2, /fat32-0 -- to the users or ftp group. Make sure that all of your users are in the "ftp" and "users" groups. (see /etc/group) Make sure that whatever group owns the directories has read and execute permissions. chmod 750 ./directory -- should do it. (You will probably want root to own the directories)
Set up a private area with a file path like--
/home/ftp/private/ -- then the 3 directories above
Then set a group for anonymous, make sure that /doc_tutorials & /uploads directories are in the "anonymous" group. Make sure that the ftp/anonymous user (see proftpd.conf) is in the "anonymous group". Again chmod 750 should do it.
Set up an anonymous (public) area with a file path like--
/home/ftp/public/ -- then the 2 directories above
One side note: IT IS VERY BAD TO LOG INTO AN FTP SERVER AS ROOT--ftp sends passwords as clear text. IT IS ALSO BAD IDEA FOR ANONYMOUS USERS TO HAVE UPLOAD!
A better solution is to set up a special group for uploading and only put those users that need to upload in that group. Then set permissions like chmod 770 ./directory (with root ownership) If you must be absolutely be root, use scp or sftp.
Beyond all the unix file permissions-- proftpd.conf has many options. One is (I think, I'm on a winders box right now)
Stick it in the global. This sets the users starting directory as their change root. Thus if the "anonymous" user on your system has a home dirctory that just contains just /doc_tutorials & /uploads then thats all the farther he will go. This directory should be below the starting directory. His (their) home directory should be /home/ftp/public in this example /home/ftp/public/uploads etc... For a global (who you called "root") user (who needs access to both sets of directories). The home directory global user should be /home/ftp
Other users could have their (not a great way) home directories set to /home/ftp/private -- this would be kind of a pain if they have real shell logins...
proftpd.conf has anon config examples in the file -- you will have to set up upload areas for your uploads. See proftpd website -- hehe I have to get back to work