You've left him open to so much abuse there. I love it. Nipple clamps - if tied to a support above him would help the slouch but I would want to torment him as well. As you're very ingenious can you arrange for him to have to hold a rope with his teeth so that, if he lets go, a weight would then drop to make the clamps tug upwards on his tits.... then - he's open to tickling everywhere almost. See how long he can stand it without unclenching his teeth. That and the wand to his cock (which appears to be enjoying itself too much) - you might want to discipline that.