I'm not sure this is going to be definitive, but it may certainly be informative.

001: Yes, with the same suggested change as Djinn_In_Tonic proposed.
002: No, I don't think something as abstract as metamagic cost reduction applies to this thread, unless by RACSD you just mean "Common Houserules."
003: No, see 002, and this one isn't even overpowered in most cases. This one I could see how it might not have been intended, but we're in the land of new acronyms.
004: Yeah, sure.
005: Yes, though this is one of those rules that everyone uses anyway.