1. Thieves' tools will contain 10 charges. Without proficiency, it will lose a charge every time it fails. With proficiency they are only expended the second time a lock pick fails. The first time the user is "extra careful". This is a Dexterity check so there is incentive for the proficient user to go first and for the one with the highest dexterity to try with coaching from the proficient user. On next level up, thieves' tools proficiency can be granted to the helper if they choose.
2. Using the tank as a shield: When standing in a doorway, hallway or gap, they count as full cover to anyone behind them, that's already vanilla. However, those behind can cast offensively and use ranged weapons "through them". Like shooting an arrow past their waste or casting by pushing hands through gaps in their coverage. This is my interpretation. Their Freya was able to cast Burning hands through Bear with a 90 degree fan as normal without exposing herself directly, then she ducked back into the room behind him on her turn.
Caveat, though ranged attackers can't target those behind if a ranged attack misses the tank, it has a chance to hit the next in line if they're directly behind. The way SheShe's group handled it was to have Bear block a doorway while they would fire from behind him then duck out of the way as they were firing from one room to another. If they were in a hallway, even only 5 feet wide, they could shimmy past each other to attack and then leave the 2nd tankiest one to absorb the potential misses. The tank would act as 3/4 cover at that point or a +5AC bonus. The strategy is not as effective in open combat as the shooter could just gain a clear shot if they can get at least 45 degrees offset. Half cover for half that and so on.
