Yeah, he does know one, though I wonder if it would work very well here. Silencing himself would work very well, and he really should be doing it. I guess Paolini didn't have him use it because he thought it would make this scene tenser, but making Murtagh competent would do more for that.

God I'm tempted to post the chapter I wrote in which my own character who has magical abilities infiltrates a place. That character even canonically has ADHD, and he's ten times more competent than Morontagh despite his impulse control problems because he's, y'know, smart and resourceful. The tension comes from the fact that there are magical traps and hostile magic-users around he has to get past. He sure as hell doesn't trip over his own feet and waste time staring at random spiders.

I think that one might be because Paolini thought it sounded tense (and it kind of does, but Murtagh is not going to have much trouble now).

Paolini definitely thinks breaking things up with ellipses makes it more tense.
Guess what. It doesn't.