1. Can I have the link for instructions on porting the Roy/Ike PSA over someone else?
I likes my Ike, Marth and Roy :3 (Mr.G&W, on the other hand...)
libertyernie answered questions 2-4, so I'll answer your first question.
There is no need. Port Roy over Ike, and then port Ike, using the generic .REL over top of some other character. Right now I have, on my system Roy over Ike, and then Ike over Wolf. I can have an Ike Vs. Roy Vs. Marth match by having selecting Wolf, Ike and Marth, respectively, on my Character screen.
Marth is VERY PICKY about what characters he goes over.
EDIT: Actually, know what? Here are the instructions on how to patch the Marth .REL.
At the Address 0x3, put the .REL Id of the character you're going over
At the Address 0x14E8B, put the .REL Id of the character you're going over
At the Address 0x16E, put the character Id of the character you're going over
At the Address 0x237, put the character Id of the character you're going over
At the Address 0x18AF, put the character Id of the character you're going over
At the Address 0xA507, put the character Id of the character you're going over
At the Address 0xA56F, put the character Id of the character you're going over
At the Address 0xA5CB, put the character Id of the character you're going over