Ironsoul:
I'm more on the fence with this one thatn I used to be, but I still think its a bit of a stretch. He is an evil dude, and he still looks like a human in the POV JE. A Blasted, tortured, and burned human perhaps, put still walking upright and without horns.
I would think that something as powerful as TJE appears to be, that it would be able to reveal his true form.
That said, maybe not. It could be that that kind of damnation is unprecedented in a human who has been alive for only a few decades. We know that (non)men have traveled to the Outside in the past and have been possessed somehow by Ciphrang, and we just don't know wtf Kellhus did out there. Maybe he went in with 2 human souls (his own and Kosoter) and came back with his own intact in exchange for Kosoter's.
Which ever of these two explanation is less obvious is likely closer to the truth, but I haven't any idea which one that may be. Lies and mysteries.
Ishual and Sranc:
First, Mimara got her Chorae from a dead sranc, so its not terribly unlikely that there where a couple in those large mobs that had them. It is, however, a bit odd that there are so many sranc in their way, since Ishual is far northwest of the Ordeal... Or is it? All the sranc in the North seem to either be drawn to the Ordeal, or mobbing in front of it once they get there. Given the circumstances, it doesn't seem terribly out of the ordinary.
Once they get to the snowy mountain passes the sranc disappear, which seem reasonable, considering Ishual was never under sustained attack from sranc (that we know).
Skin Eaters:
No idea what the end game of this was (or what it was supposed to be). Sacrificing Akka doesn't seem likely because of the huge foreshadowing at the end of TTT, but Mimara is a disposable pawn to Kellhus at best(if he is unaware of TJE), and a liability at worst (if he does know). Using her to turn the Nonmen King to their side, as a contingency for whatever Serwe/Sorweel are doing, is a good idea.