Pitch it. Regardless if it works or not, or is sufficient in terms of wattage, the "generic" P/S (especially the ones that used to come as a freebee with a case) are complete garbage. The P/S is the single most important component in any system, as everything else depends upon it.
Yes. The parity drive though has to be as large or larger than the largest data drive.
Yes. But, for SATA expansion cards, it is best to avoid any card which is Marvel based. LSI / AsMedia would be the go to's
Yes