So looking through it. To get a few things out of the way:
“Nulmor,” the stocky man glanced at the hall-master with a grin, “you need to shut the door tighter.
Rats are one thing, but who let this half-blood in?” <-- I know you're avoiding "he said" with all your might, but you got your beats and text tags mixed here, so do not use commas.
"“Nulmor.” The stocky man glanced at the hall-master with a grin. “You need to shut the door tighter.
Rats are one thing, but who let this half-blood in?” <- like so.