Some things I learned as of 0.51.1:
You need 15 in charisma to bring all 5 available members with you. It's a gradual increase. 7 charisma lets you bring 3 companions and 10 lets you bring 4.
If anyone is concerned about maintaining your hunger meter, I recommend making scavenger pies. It's easy to grind for the ingredients, cost effective and it recovers 20 hunger with 50-60 HP. For healing, you're better off just buying curingpods (you will be able to heal 120 HP with 7 intelligence) or mre (hunger + more cost effective), since the better food items all require ingredients from monsters that rely on rng to appear.
Water is free in nogas (if you fought off the slaves, 3 grams before then) and last Elysium. It costs 5 grams in greyfold, 10 in babili and 8 in shine town. Food is 5 grams in nogas (40 HP 20 hunger) and greyfold (50 HP 25 hunger), 20 grams in Babili (40-70 HP 30(?) hunger) and 15 grams in shine town (100 HP 40 hunger).
Sometimes, the game may ignore any increase in your base constitution when nurturing your health. In one save my health went from 140 to 130 when nurturing in greyfold despite having base 7 constitution (low hunger + Kay T training). In another, the health stat would increase according to my constitution stat. Also for some reason when you add points into the constitution stat in character creation your hp increases by 20 per point but resets to 10 points per point in base constitution when you nurture health during the game.
I don't know what triggers this bug, but in two different saves, when I am grinding for ingredients in greyfold, my thirst and hunger meter would suddenly stop increasing. The first time it occurred I also lost the ability to collect money from the assets, so when it happened again in my latest run, I just straight up reset.