Oh my... that is a lot of questions @_@ Er... *switches to dub names since that's what you're using* ._.
Malik turns into Yami Malik after Rishid/Odion (I think that's his name in the dub o_O) is defeated by Jounouchi. Rishid was kind of like the "seal" keeping Yami Malik in, so with him unconscious, Yami Malik took over. That was just before his duel with Mai. Omote/Normal Malik didn't take over until the end of the duel with Yami Yuugi and Yami Malik.
The only "good guys" who Malik took over were Anzu, Jounouchi and Ryou. @_@ And... lastly, yes, Kaiba lost to Yami. o.o;