Haha - loved the end of this - brilliant. The rhyming throughout this piece is very good, too.
My only suggestion would be to break the poem into more palatable segments or stanzas, but that's just personal taste.
Also, "after all I've done" would keep the rhyme with "gun" but make grammatical sense.
I love that line, though - likening his nerve to a kid's playing Russian roulette "with a fully loaded gun".
Well done and all the very best,
Ben