Also, I'm slightly confused at how he's being portrayed in this chapter.

I'm not. It's easy enough to say that "character X is Y", but what does that mean ? The motivations of character Y in HP:MoR are very different from what they are in canon. Merely knowing the label "Y" tells you very little; the greater mystery is not what label we should apply to X, but what his goals are, and what actions he has already taken, or is planning to take, and what his overall grand design looks like. Everything we observe the character saying or doing is evidence that can help us expose this design. His canon counterpart's actions in the original HP books, on the other hand, are not.