Hi Lynne,
He says it because he is insecure about himself and does want to exert control over you and your relationship with him.
This is where he feels powerful.
When he taunts you by asking you if you think that you are the most beautiful woman in the world, he likes it when you get upset. It makes him feel powerful.
So yes, as you stated, he does want to get a reaction out of you and he does want you to seek more validation from him.
All of these things put him in the power position and thereby he can manipulate your emotions whichever way he pleases.
This is mental and emotional abuse.
You should leave this guy before he drives your self-esteem so low that you are psychologically damaged for good.
He may move on to other relationships but you will be left with the emotional baggage and this will negatively affect your future relationships going forward.