Maybe a "little"! But you gotta admit that the music really tells you that a Battle between "Good and Evil has arrived" so i think the music suits him in some way!?? P.S Sorry that i didnt answer you before now! I was blocked!
Which ever you think is best. I believe your KH selections good so far. Personally I like to eithe rcompose my own pieces or at least consider remixes of old MLP G1 music or something. But since not everypony is musically inclined I believe what you got so far for KH themes for Nemesis is good.
I think you should choose what you think fits with Nemesis best. Think about what kind of character he is, imagine what situation his music will be best in, things like that. I can give my oppinion on which I prefer or not but I don't want you to feel you have to fold to your audience and not be yourself.