0 Max Durability For A Weapon

If a weapon were to lose all of it's max durability, due to repair failures, would it be unequipable, or always equipable?

Unequippable, unless you had it equipped already at the time of the repair failure I believe. The only exception is magic powders. Even if you have it equipped though, your damage will be as if you were barehanded, and enchants on the weapon will not activate. I'm not sure about reforges though.

All reforges on the broken weapon will stop working