Did the Jackal Kill Quinn?

The Jackal admits it himself that he pushed a sliver of Quinn's skull further into her brain, killing her.

Is Sevro really dead?

Sevro is killed, and his body is brought along. When they arrive, they see that the Jackal is there as well as Aja.

Why did Roque betray Darrow?

Roque loses faith in Darrow, believing him to not care for his friends and to hide his true intentions. He betrays Darrow after discovering him to be a Red, and condemns Darrow to captivity and torture.