As for more world-building -- it's a little hard for me to say since I already knew a few things about the world before playing! I recommend finding some more playtesters -- you can DM Jess, who will be back this weekend, and I'd suggest posting it in our class Slack channel too. I'm sure there are folks who would read and comment on it here.
I do suspect you'll need to explain the world not long after the current ending -- but leaving the "regular" and "unique" parts mysterious before that make for an interesting "this is a strange world, but I'm not going to spell it out" tone that I think could work to tantalize readers.