Changes

The approach to the water requirements should be conservative, i.e., over-estimate the capacity required. Potentially this could be an energy inefficiency but you will prefer that to an insufficiency of water. It’s a good idea to decide the water system before finalizing the plumbing system.

The literature on water consumption is all over the map. Experienced yachtsmen on cruising sail boats can manage on 1.5 gal of water per day per person, for all needs excluding bathing and dish washing; although 3-6 gal is more common.