My question is, in the episode 'Fascination', whether Dax's passion for Sisko stems from Jadzia or from Dax. Hmmmm.
I believe it's from Jadzia. While not canon, the novelization of "Emissary" did say that the Jadzia host was privately attracted to Sisko, something that the Dax symbiont may have found amusing. "Fascination" seems to have played onto or coincided with the earlier idea in the novel.