Interesting that in the survey they have 2 specific questions for ch.5 and 6. I think ch.5 is not necessarily bad, it doesn't really shine either, feels more like a rush to tie up loose ends. Ch. 6 however, is not a chapter and, Jupiter forgive me for writing this, it makes House at the End of Time look good. Surely, I'm being fabulously optimistic here, but maybe...
Suggestion 1: commission more portraits. Weird how a character as narratively insignificant as your quartermaster has a portrait while others like Zacharius have to go without. And the FemAzata desperately needs a portrait that doesn't make her look like a stageplay extra.
I acknowledge your agenda, but the only true answer to the portrait problem is not have more of what already exists, but delete everything and pay whatever the fuck it takes to Justin Sweet to remake the whole thing.