I've reached the end of what's currently reasonably achievable in about 10.5 hours of playtime. I may throw myself at the currently-unreasonable grind towards crafting a Soul, but otherwise I'm "done."
My main feeling about the game as compared to other "discover the mechanics" incremental games, like The Candy Box 1&2, A Dark Room, or Universal Paperclips, is that there's just not quite enough to discover after Darkness. You know that much already, though, so just call that a +1. Don't be afraid to throw a massive curveball at the player's assumptions and/or completely change the main genre.
The Hermit, Strength, Temperance, and The Magician seem to be the only charms you really need to start grinding. The Emperor is an obvious first choice for housemaxxing, but Strength seems to overshadow Population management, especially if you also have The Heirophant. I really quite like the charm system, but they definitely spiral on themselves rather quickly.
I definitely agree with every point in the TODO list. I think that giving the Heart a tally of how close the other resources are to Infinity alongside food might make it more intuitive that you should attempt to max out all 16/18 resources to get the maximum benefit. Also, a button to exit from the game to the save selector would be nice, unless there is one already and I just missed it.
10/10 game, can't wait to start a new save file on a future versions.