Q30: What prompts Dio to pull a knife on Clover?
     And why leave her and Tenmyouji alive after handcuffing them?
     Why not kill them with his knife, instead of risking them being found?

     Well, originally Dio was planning to do something even more messed up to Clover, but our president said NO to that idea for ethical reasons, so that scene was cut out.
     That’s why Dio pointed his knife towards Clover. The reason why he handcuffed Clover and Tenmyouji is because he enjoys the gambling feeling of it all.
     Experiencing luck and winning in that type of game is the only way he can sense the feeling of “love”. Just think of it as the mentality of a messed up person.