The sentence that best reveals Fabio's feelings through indirect characterization is:
"So, Fabio sat alone in the band room and wailed out the Rocket’s fight song in a minor key on his lonely saxophone."
This sentence reflects Fabio's emotions by showing his isolation and sadness, as he plays the fight song in a minor key, suggesting a sense of longing and disappointment due to his broken leg and separation from the excitement of the other band members.