I'd leave chunibiyo in Japanese. The only people who know what "8th grade syndrome" is, already know what chunibiyo is. To me it is similar to translating karaoke to empty orchestra.
It was already shown how being stabbed with your own sword works. If the swords function as you describe, Tsuchikure would have turned into a regular gun after their first fight.
He really decided that: the explosion wasn't realistic enough for his cartoon, that takes place in fantasy world. You can really feel how much Tsurusaki and Ikezawa love the manga they have made.