1. Yeah, fair enough. I would point out that he has all of Naga Sadow's knowledge, but so does Freedon Nadd. 👆
2. The text made it intentionally vague, but it seems to either be because of the dark side nexus of the world or Freedon Nadd was intentionally suppressing his abilities. I don't think it would show Nadd's dominance, however, since he was already a Sith who had access to the planet's power, whereas Exar Kun was cut off from his power since he still was a Jedi and wielded the light-side, if that makes sense. When Exar Kun embraced the dark side, we saw him destroying the Massassi en masse.
3. Actually, Freedon Nadd was a Sith for a *century*, in contrast to Kun's year. Another point in Freedon Nadd's favor. 😉
However, even if Freedon Nadd has greater mastery, knowledge, and experience, Exar Kun *does* have the edge in both power (based on feats and the "most powerful"quotes) and lightsaber abilities. I muse (it's hard to really tell when dealing with characters like these, so speculation is needed, if you ask me) that said factors would be enough for him to best Freedon Nadd (which just makes sense to me, since Kun blasted his ass out of existence), but I think your arguments here, at the very least, show they're close. 👆