As far as your speed requirements are concerned: forget it. Even on a Gigabit network with only one single consumer, the Sharespace seldom exceeds a read speed of 10MB/s
Write speeds are even worse (max. 1-2 MB/s when writing many small files)
FTP is easy: just enable FTP in the GUI of the share.
Security (read-only for users) is done in the user config: just create a user, then switch over to the share management. That should show you your users on the left hand side and Read, No access and Read/Write on the right hand side. Now you can just select the users and switch them over to the “read only” column. Save + you are done.
I do the same thing you want with my 4 TB NAS (RAID-5). I can easily access the movies stored in “Public/Shared Videos” by means of my TV. So that works fine, too.
My Music is on a special share called “Music” and I access it through my Sonos Streaming-Clients which have a read-only user to this share (and this share only).
I also activated FTP on my personal share so I can transfer files more easily and reliably by means of Filezilla. (I don’t trust the Windows Drag&Drop thingy too much when I want to transfer large directory trees)
So except for the speed issue (which can’t be solved because the Sharespace **bleep** performance-wise and WD does not give a cr*p) you should be able to do easily what you want to do.
Just browse through the pages in the “Advanced Mode” of the admin interface - you will notice that it is actually not that complicated and mostly logical when it comes to navigation and page hierarchy.
