The only other dimensions of similar age to Teenyweeny (that we know of) are the Maelstrom Dimensions where Cyclone, Kate, and all the other Nexus Figures are quite dead. In SOTS I believe Demonstrait shares that Maelstrom Dimension policy on Nexus Figures was to just kill them, instead of trying to infect them. They do change their mind and infect Janitor Cyclone, though, but this is the exception. Charles hinted to this in Ch 16 when he talked about how Teenyweeny Cyclone and Kate are the only remaining pair of them, as the rest have been hunted down or maybe never existed. For instance we know there was a Janitor Cyclone but maybe there's no Janitor Kate. The Janitor Dimension is rather screwed up in other ways too, with Sandy Studs getting killed in it as well and Janitor Cyclone on the verge of getting killed, until Flumberfluff Kate saved him.
Teenweeny Charles takes the place of the Charles that would have existed in the new dimension's timeline. I'll share the story isn't finished with that dimension, and its existence is not that dissimilar to Aiden's personal dimension...
Chapter 18 has been redone. A new formatting method also serves to differentiate between the flashback and present scenes. The explanations in my earlier reply are now integrated into the chapter itself. I used the opportunity to include some redundancy between Teenyweeny Charles in Ch 16 with Cyclone. I think you will find our hero exonerated and quite sensible in his decisions now. :P