I disagree...for them to successfully stop 'feeling', they must be able to distinguish feelings they see on each other's faces...a bit like you cant write anything meaningful without knowing how to read...Kellhus is fallible definitely...but i'd say his fallibility 'reduced' as he got older and learned more stuff...i believe his TTT took into account the Gods and even the necessary sranc-eating...Did he get deceived by Yatwer? I doubt it...even if Kellhus saw every sign of sincerity on his face, there's no way Sorweel could have turned so quickly and so completely...He anticipated the Gods' interference and thus he would be on the lookout for any weird stuff among the Believer-Kings...
I agree with pretty much all of that, expect that framing it as "kellhus' TTT" might not be technically correct, but does establish the spirit of what you are saying. Just as TS pointed out:
We never actually see Kellhus grasp the Thousandfold Thought, or understand what that means. All we see is Kellhus deciding he's grasped it.
To me, TTT is just a different way of describing a deep delving into the probability trance, but this definition is hardly the most accepted one. Whatever you want to call it though, what you have described seems to be plausible.
Also, we know that not only Kellhus can see that something is wrong (or at least 'not right') with Sorweel, but also his children, who are only half-dunyain. If Serwe has a mini breakdown trying to discern his true feelings in TUC, then I am 100% sure Kellhus knows something is wrong and is/will be re-formatting his plan to take him into account.
Does Kellhus know the Gods will vie against him? Absolutely. Once he knew that the Gods were actually real he must have come to that conclusion. That doesn't mean he knows exactly how, who, where, or when they will try to interfere, it doesn't mean he knew that Sorweel would become an agent of Yatwer or any other god, and it certainly doesn't mean that he has plans in place to counter every move they might make. What it does mean is that when something like Sorweel shows up, he won't go into ultra-panic mode and shut down.
If nothing else, Kellhus has an acute mastery of the probability trance and has spent decades planning this war. Therefore he has a spectacular ability to plan moves far in advance and will have many contingency plans in cast events don't go the way he originally hoped. The trouble with the probability trance is that its a function of... probabilities. Think back to Moenghus, who had some 30 years to plan. Ostensibly, he failed to consider that Kellhus would come to him "mad"/"broken" from the journey, and it cost him his life. Maybe that was a sure bet, 1 million to 1 odds that Kellhus would break, or maybe it was 50/50, doesn't matter. When something so fundamental goes wrong early on and is not discovered until late in the game, all your planning is for naught.
This is certainly a huge weakness when coupled with the fact that Kellhus is really bad at noticing his own faults/errors/shortcomings, which leaves an opening if things don't go the way he has meticulously planned.