I have some thoughts on water. Our solution is to have a big, clean river running through the property. But the backup plan is that we have rain collection barrels, and the water from the well pump goes through a storage container before it goes to the house system, so that is another 250 gallons that stays in the system if the power fails.
But one thing we did when we lived on the sailboat is that after we filled the fresh water tanks, we would pour a bottle of vodka in for preservation. We used 1 bottle per 400 gallons, and that worked for us, but I don’t know the optimal proportions.
My son has told me that we should have on hand the components to replace the electric well pump with a hand pump or windmill if needed. Probably a good idea.