King doesn't like to torture people. It's Queen who does. And it's Queen who called him a torture-loving pervert in the first place, probably insinuating he liked being tortured at Punk Hazard due to his durability.
Where did you see him enjoy torturing people? Even when he needed to kill Momo he gave an excuse. He offered Sanji to let go of him if he leaves before he slammed him into the wall. When he burned his subordinates it was self defense. He goes straight for the kill, he was never seen enjoying watching people suffer.
And back to the first question of this thread - I believe King will find himself helping Luffy eventually. It might require a cover story or something, but I hope for him that his childhood dream of joining Joy Boy would come true.