Dante embraces both, his human and demon half in DMC3, all this you're syaing just means you never played it, or just skipped all cutscenes.
Specially when you said Vergil wanted to obtain the power from an "ancient evil" is just worse. He wanted the amulets so he could open the gate to hell so that he could retrieve the Force Edge, Sparda's sword, because he needed that power, without it he wouldn't be able to protect anything.(He even says so to Dante).
in DMC3 dante seems to resent sparda for not being there
Until he fights lady and starts to acknowledge his father's legacy after her speech to him about "family business". At first he hated what his father did but at the end he started to care and knew how important was his father's legacy in the settings.
Oh, and when I confronted him after the game came out about it not being chapter based, he started telling me that he never said this game was chapter based and that he was talking about MGR. But here we see proof that he was, indeed, saying that DmC was chapter based.
Didn't he come up with some excuse about the storyboard being chapter based or something like that?