i would think he'd be an ixfj for sure. i can't imagine an istj singing hurt? plus my favorite songwriter ever david berman of the silver jews way reminds me of johnny cash. and i think david berman is either an infj or maaaaybe an infp. he's way more poetic and metaphoric tho, so i think i'd actually put johnny cash as an isfj. more of a troubadour fj thing writing about and to and in between others rather than from the i'm johnny cash and these songs are ME. seems very Fe.