Race to the End of the World question

Loved the book. I can see why kids would love to read it. Unfortunately I'm an adult and I want explanations of technical matters to gel with my experience/powers of analysis. So here are my concerns. P.7-8 Quinn escapes the dungeon at scribe school. Ignoring the fact that no dungeon builder worth his salt would give a prisoner access to the screws of the hinges by putting the hinge on the inside of the room! We are left to visualise Quinn and Ajax on the outside putting the hinges back on the door. Hinges are at best only ever accessible from one side of the door. (Modern doors have them hidden away from prying fingers inside the door frame.) Given this unfortunate fact the boy would have to go back into the room to fix the hinges....leave through the door normally..and lock it behind him.
P.148 I have a similar problem with the nails made of wood... unless you drilled holes into the table top first the 'nails' would shatter when hammered. And why did the legs have to come off? Upside down with the legs lashed together the boys would have had a stronger bridge. Ajax instead weakens the table by leaning on and smashing off the table legs.
P.187 Ash receives a good kicking. P.199 she looks in the mirror and sees a bruise of black surounded with purple-green. This bruise seems to have developed in one day. Perhaps readers will tell me such details do not detract from their enjoyment. I hope that is the case because i did enjoy the romp. Cheers. K