First Question: The ADDON cd is just that, an ADDON to Other OS's (not Yellow Dog, more fedora etc)
Second Question: You probably could, but it would be such a hassle, would really not be worth it. Considering that YDL is based of Fedora Core, not much of a difference.
Third Question: The programs need to be specifically compiled for the PS3 (most of the time).
Fourth Question: Yes it should, just grab a version of Fedora Core (x86 or x86_64), format and install, your set! You can dual boot, its a bit more tricky, and yes, it boots just like windows does (from the bios etc)