@LOH on #3)
IIRC, didn't Uthar Wynn in K1 have some sentiment denouncing the concept of love? Isn't this what has more or less proven to be what ultimately separates good from bad--what the difference is between mostly and fully embracing the Dark Side? J7 above got to it before I did.
I'll agree with you being a sith in and of itself isn't what ultimately decided whether folks were bad or good, though.