The two Venom LiPo containment boxes I designed were ment for up to 60 Watt Hours.
That means any pack configuration up to this specification is ok when the pack fails inside the box. The box is meant to allow the pack to out gas and smolder but not explode or project fire. The box has ventilation but the pressure exiting the box will prevent the atmosphere from entering immediately and feeding the fire with fresh oxygen. That is what keeps the event contained inside the box. The lithium material will feed off of oxygen in the air and from water so it has to be snuffed out. I blew up over 12 packs of various sizes in one container featuring a polycarbonate window with no failures to the box. The box was discolored and window was blackened but the situation was contained with no collateral damage. The smoke is horrible and will stain the area with scent and soot.

In terms of storage your container, like an ammo box, is not the best idea but it will do for 2 or 3 packs maximum as long as they are 2 or 3 cells a peice. For larger packs 3 cells and up these should be isolated to one container per pack ideally.

Do Not Store all of your LiPo packs in one container. Spread them out over a couple containers to prevent a runaway fire situation and potential explosion.
LiPo packs EXPAND to 4-5X's their size when they fail. If several of them are in one container they will probably burst the container and effect anything surrounding the immediate area.

Also what keeps a LiPo pack hot after the fire is over is the many sheets of copper that make up the individual cells. These will be very hot and will contribute to the fire situation.

Storing of LiPo packs should be done at the nominal voltage of 3.7VPC. If not the packs chemistry will cause more internal resistance, poor performance and loss of capacity. LiPo is not the best "storage" chemistry. LiPo is designed for cycles not storage. For storage applications use LiFe.

LiPo packs fail in a couple of ways; cold and hot. A cold failure is a condition like a steady trickle discharge until the pack is dead. A hot failure is typically when the pack is under load and pushed below 2.8VPC. In both cases it is likely that the pack will balloon, an indication that the chemistry has out gassed. At this point if its a slight puffing up and the voltages across all cells are normal it is likely the pack can be used again but it should be watched closely. Typically a dead pack will not recover.

The Boeing pack failure is an intesting case. They used Yuasa from Japan who to my knowledge has little experience in Lithium Polymer battery tech. Their expertise has been for decades in lead acid and gell cells typical of cars and motorcycles. They should have used BYD from China but I'll bet their relationship with ANA Airlines had something to do with their sourcing decision.