It seems most likely that those Fused are dead for real. Nightblood wrecks things pretty good.
@Journey Before Pancakes realmatics is far more interesting than gender.
Brandon said ages ago that the Lord Ruler would have died if beheaded. He was only partially decapitated.
But we have WoB that gold healing CAN heal a Shardblade-cut limb.
Personally I think Bronze feruchemy would be hella useful, but then I have issues with my sleep schedule that I could fix by storing when I'm supposed to be sleeping and tapping when I'm supposed to be awake.
I agree with @Calderis, I do not see anything inherently religious in the Radiants' oaths. They are just a a set of philosophies for how to live, except for the Lightweavers, which are about self-awareness. They can exist independently of religion.
Yeah Nightblood isn't really useful in a traditional fight. He's good for taking out mooks who are susceptible to him but he's not going to be much use in a duel with an opponent who is immune.