Excellent choice of Public Domain work to start from! A "narrative adventure" sounds like a great fit for it.
I wonder about the feasibility of npc-scheduling in a first-person game (at least, I've heard various devs remark on the unexpected time demands scheduling in general, and first-person perspective seems like it tacks on additional content costs) but the scale of everything (total time, total possible activities/locations, total characters, level of detail, etc) is probably a major deciding factor. Your choice to keep the story beats to ~5 sounds good.
I'm very curious to see what you come up with for this!
(Also: a web build would be fantastic, if it's not too much trouble!)