Oh man, now that you mention the balls thing… I’ve always pictured Jack having a scent kink. He loves the natural smells of a man, especially after they’ve worked up a sweat. He starts stealing bits of Gabe’s gym clothes to smell while he jerks off-a sock, pair of underwear, maybe even a shirt if he’s feeling daring-until he finally gets caught one day. He ends up spending some time with his nose buried in Gabe’s crotch and armpits after his next workout and he’s in total bliss.