The name "30 coins" brings to mind 30 pieces of silver, and the "Musket of Longinus": Isn't that a reference to the spear with which Jesus's suffering was prolonged on the cross?
The French name actually is the translation for the "30 pieces of silver" (30 deniers) that Judas received for betraying Jesus. I'm assuming "30 coins" was chosen for its brevity, unfortunately that also makes it lose the direct biblical reference. The musket is certainly a reference to the holy lance of Longinus (although I think it was used to show Jesus was dead rather than to prolong his agony).
However there's little information as for who this guy actually is. His fluff in the book is about his thoughts as he chases and executes the last, 10 year old survivor of a caravan he was hired to kill. There's reference to betrayal in there as he had joined the caravan before eliminating its members, and he does mention that he only does that for money. Also I guess his ending the agony of the 10 y.o. boy (who already got a bullet in the belly) could be another analogy to the holy lance. But unless I miss something there's no clear hint of his being either Judas Iscariot or Longinus.