I'm also interested in what problems you have with the official translation. Not taking a jab at you but I don't see any significant differences between your translation and the official's for this chapter. I would say I prefer your version more just for the addition of translated sfx's but it's...
Interesting to see where his "I'm immortal" mindset originated from. Wasn't even from the war but rather further back.
I'd like to add that Boutarou is a subtle foil to Sugimoto; both have a strong will but one lives for himself while the other lives for other people.