I did not catch that he didn't take the chorae with him.
+1.... I'm sure that will be very important later. An undetectable chorae in the midst of the Aspect Emperor
Regarding sranc:
Depending on what year it is after the fall there could be huge differences in sranc population. Consider first: distance. based on what we know, all of the sranc were drawn to Mog, not to mention that all the humans in the world where pretty much in the same place. This places all of the sranc west of 2 mountain ranges. Once they 'killed' the No-God, they sranc fled. Well how fast did they flee? That depends on how pressed they where. We saw the Ordeal push the sranc thousands of miles in a short time, but I doubt the living humans did much more than passvly hunt the sranc. It may have taken years, decades, or even a few centuries before the sranc where pushed back to the North.
Once the sranc where confortably past the edges of civilization, they then probably bred extremely quickly. They would have greatly reduced numbers for years, but with no real predators and ample food (grubs, worms, etc.) it would have been an exponential population explosion. Depending on what you want to do with your story, you could go from barely any sranc to hundreds to thousands in a time span of a few centuries.
Also recall that sranc are drawn to certain places over others. I think ancient ruins draw them in for some reason... remember those ruins that sorweel and his horny friends end up in where someone mention to be carful because sranc are "drawn to places like this" or some such? Sorry for the vague reference, my point being that some places could be strangly empty of sranc while other places close by could be teaming with them.
You can probably do whatever you want with sranc and their numbers and there will be plenty of reasonable justifications for it.
Siqu:
Madness covered most of it. As for whether or not there were any left... probably not many. Intact Nonmen might be slightly more common close to the fall of the NG, so there might be some tutors left roaming around.
Diamos:
Nothing consolidated. Iyokus might talk a bit about it during/before his little tussle with Super Saiyan Achamian in TWP