Read the Darth Plagueis novel if you want a more human version of Palpatine. Also one does not need a reason to want to rule the Galaxy as wanting have dominion over people is a reason in of itself. Some people are just controlling.
Still sounds better than his characterization in ROTS.
Not by much; that’s why I prefer the novelization. Even something like Anakin being denied the rank of Jedi Master (which is glossed over in ROTS) is quite profound in ROTS.