Well, it goes kind of like this: (play the music to get the full effect)
1. No. No one knows who Nero's mother is. The people on the island of Fortuna assumed she was a prostitute, because she abandoned Nero on the steps of an orphanage.
However, since Vergil is attracted to power, and since Nero is (presumably) a quarter demon, the human must have been an
extremely powerful witch, like Eva was (again, presumably, since the only one who said so was hideki kamiya).
2. Nero is (presumably) a quarter demon, since he was created by a half demon and a human. Also, Sanctus said that Nero had "the blood of Sparda in his veins" but wasn't as "powerful as Dante" (when he said that he should have stuck to his original plan at the end of the game).
3. According to "in-game canon" Nero is
physically stronger than Dante (because Dante said that humans have something that demons do not, which is
presumed to be... love, I guess? :ermm
However, I don't think he has as much demonic magic in him as Dante does. Strength doesn't necessarily equal power, especially when you're talking about magic, from my point of view.
---------------------------------------------------------
Bonus:
Bayonetta and Metal Gear Rising have great gameplay... but I absolutely hated their stories. And some people have said (I won't say who) that MGR doesn't have "that many combos". Their words, not mine.
---------------------------------------------------------
However, I didn't like either games in comparison to DMC3 and Darksiders 2. This is just my personal preference, so play what you want, and keep what you like.