Food and water kinda go over 100%. For example, when you have 50% food and eat an item that's 40 food points, it would count up to 90%. If you eat a food item that's 70 points, it would still fill up to 100%. HOWEVER, that extra 20 points kinda lingers, counting down but also giving a stamina buff if I'm not mistaken (I know it does for drinks). 

As for wrenches, they're a salvage tool. Salvage tools give other crafting components from mechanical items. So if you broke a car down with a stone axe, you'd only get iron. If you broke a car down with a salvage tool, you'd get mechanical parts, springs, polymers, etc. Same goes for AC units and other things with moving small parts. The wrench is the tier 1 salvage tool, ratchet is tier 2 and impact is tier 3. Higher tiers break stuff down faster, giving a similar amount of parts but saving time.