Zack Fair

I don't think, he does. But maybe he over heard Terra and Aqua speak, or maybe he just figured, that Eraqus is gone.

To your first question, then JTD95 has already answered it. Second Question: There are many ways to make Kingdom Hearts. Collect the 7 princesses of light, destroy Heartless (Emblems) with a Keyblade. I also read in a Xehanort report: The Kingdom Heart we see in the Keyblade Graveyard was probably created during the Keyblade war. Master Xehanort just removed the skies.

I doubt he will continue his English playthrough, since Final Mix will be out soon. EmiruTheKnight has completed both Terra and Ventus, he is currently doing Aqua's story: http://www.youtube.com/user/EmiruTheKnight#g/c/2DEEC5C6813EE131

Xemnas is Xehanort's Nobody, and Xehanort: