I don't think it's particularly creative, but try to carve a knife out of the Obsidian because I'm pretty sure it's stronger more durable than a metal knife? I'm not entirely sure about that because an Obsidian knife is entirely impractical, therefor, has never actually been used AFAIK. But, just get anything sharp, is the idea. From there, I doubt it'd be hard to break the box open, if my assumptions are correct.

Attempt #1: grab knife. attempt to cut away the bomb straps. Abandon if no visible progress is made after 1 minute.
Attempt #2: tie rope to crowbar, throw it as grappling hook to try to get the box out of the shelf. Use crowbar as hammer, pliers as awl to open box. Abandon if crowbar can't be thrown far enough to reach box.
Attempt #3: douse shelf in gasoline. disassemble flashlight, carefully crack its lightbulb open, use its filament as a fire starter. (short wires instead using pliers if it's a LED flashlight). Fall unconscious from fumes.

okay, i would first hurl the canister of gasoline at the shelf. i would then use my pliers to snap the beam of wood into two pieces and then rub them together vigorously until i start a fire. then i would throw the flame towards the shelf and make sure it catches on fire. i will wait for the shelf to collapse and thus drop the box, before using the crowbar to crack it open and free myself from being covered in glitter😌. this wouldn't work in reality, but i never said it had to be realistic