There is a bug where my party size is permanently reduced to 2 extra spots.
I believe its caused by letting Julian hypnotize Felicity and removing one or both from your party before Felicity is given back.
Tested it and you can get down to just one extra party slot by doing more than once.
Seemingly at random your day count can reset and Felicity will allow another draining. Not sure what activates it, but, it last happened after visiting the kitsunes.
I do want to say that I think you've done an excellent job with the game; its very unique!