And why on Earth did Major Hayes (which is the equivalent rank of Navy LCDR) refer to Lt Reed as 'Sir'? Surely Hayes outranks him?
It's not exactly forbidden to address an inferior as "Sir", nor automatically insulting. Commodore Stocker in "The Deadly Years" wouldn't have been out of line when doing this to the Enterprise crew, either. It's probably a "visitors vs. home team" thing... Timo Saloniemi
I always got the impression that despite the rank differences, that Reed was in charge of overall security. It happens sometimes. I wouldn't be surprised if they were going to make him a Captain(naval equivalent of a lieutenant) and some exec decided the audience would think he's taking Archer's place. Old naval tradition, no one outranks a captain on his own ship. Really wasn't ever relevant in Trek though given how rarely we see CO's who aren't full captains.
In Breaking the Ice when Captain Archer is answering the school children's questions he says that most members of the crew share quarters with someone else. My guess is that only ensigns and above had private cabins.