(If your screen looks different from mine, select すべて in the menu left of the battery)
This item is probably your best bet. It raises a single character with 20% (% matters very little when your enemy does 200K dmg). All the healing items build into each other, so you need to make 1 each of items A-C before you can craft it.
The little leaf with the water drop is the party wide equivalent, but it takes an obscene amount of resources to make. Just in terms of crafting time, it's over 3 hours.
Alternatively, this item should reduce all damage to your party by 100% (no idea for how long). I obviously haven't crafted it yet, but I'm guessing based on the items before it cutting dmg by 25% and 50%. That black jacket is also the single target version.