@Turboshitter Of course. To answer your questions:
1: I don't imagine a bullet being able to kill a servant even with a direct hit to something important, if not just for balancing issues alone. I imagine that a bullet would travel faster than an arrow and the reload is both hands-free and autonomous, so a standard bullet being able to kill would probably be ludicrous, even on top of the reduced range from the pre-flintlock firearm. As for mages.. well, that's maybe a bit more ambiguous? Convenience as suiting the plot, anatomy/hit locations, etc?
EDIT: Then again, the big thing that made firearms lethal was that medical technology was behind that of weapons technology; for example, during the American Civil War, they'd just leave people shot in the torso to die because they couldn't fix it, and if it was a limb they'd just amputate the limb. In the modern day, it's a bit different.
2: From what I understand from the wiki, the difference is that Unyielding is a reduced effect from physical and mental damage, whereas Continuation is taking something that might knock him out on grounds of being too injured to fight well, effectively giving the opponent a hella advantage, and still being up to scratch; although being a B rank, mortal would still be mortal.
3: I'm happy to drop Endurance if you'd prefer it.