Hydaelyn's Blessing of Light is her equivalent to tempering. Ifrit immediately notes the oddity in his inability to temper you, then follows up by stating that mortal souls can only have one blessing - implying that Hydaelyn has already blessed (tempered) the Warrior of Light by that point. (However, do note that whatever you make of Solus stating Hydaelyn (and Zodiark) are primals, it's never been used to compel the Warrior of Light to do anything in the same way (other) primals compel slavish devotion with their tempering.)
Given Solus (Emet-Selch) told Varis he didn't think they'd see each other again in this lifetime and then walked off, before the parley... I think it's fairly safe to say the latter isn't being possessed or influenced by the former at this time. It looks like Emet-Selch is going to be an antagonistic force on the First, and whatever his grand master plan is I doubt he has the need or desire to bounce back and forth across the two worlds... as long as Varis uses Black Rose, as he says he would.
The governor of Eulmore mentions Sin Eaters are a part of their society, but... I doubt it's in much of a friendly way. On the contrary, it looks like they just feed "undesirables" to the Sin Eaters to appease them and keep the party going, rather than having them as integrated citizens. Can I stab that corpulent SOB at some point? Pretty please?