Working out will make him buff, buff as in muscly, not in tone.
As for cas... I can't recall if it's accessible when enabling debug interactions. Otherwise, your only hope is modding. Do keep in mind that modifying traits and the muscle & thinness sliders on CAS of an already existing sim will crash/bork the game (or get resetted after returning to the game, can't recall which), so there's a very high chance that fiddling with tone/implants will do the same.