He fumbles open the snack too, even though he's not hungry. He wants to live. Which is why Julian's made such a massive error here.

"And in tending to me you've signed your own warrant." The anger has faded. He hurts, he's worn out, but he's got a path to survival at least. The unfortunate fact is that the path runs through this man. "One of us winds up in the Quarry from this. There's no chance me being incapacitated for a few days around the time of the explosion is missed, and I will not protect you when you shot me." No, apparently a spark of the anger is still there. But just as it flares up it's gone, because there's only one ending if Julian goes to the Quarry.

"You will die for this, because I refuse to." He regrets it. Regrets that it's necessary, at least. Life will be a little emptier and lonelier without the doctor in it but he hadn't made the choice that lead them here.