The documents seem to be hinting toward keeping things our and going to a retreat(the dungeon) that was already built. All the workshops as you will notice are for building the wooden barricades which seems to imply that the area was already built as not already obvious by the age of the castle/dungeon. another thing noting the spot you start, you seem to of had dropped through the roof, bricks strewn about, dirt pile under you and the torch near your head. There also seems to be no indication that that door was ever opened forcefully due to it's appearance, and the fact that the surrounding areas are entirely undamaged. Also, there are no mining spots anywhere. at all. Not even shovels. or pickaxes. or anything of the sort to indicate that mining ever took place. And perhaps this isn't even a dungeon at all, just a castle with no windows and tall ceiling. Maybe the random spots of light with no source is light from the sky.
Sorry for not formating