To what degree does Claudius believe Hamlet is a threat to him?

I believe Claudius believes Hamlet is a big threat to himself. This is becasue of his eagerness to talk about Hamlet in act2 scene 2. But I do not believe he is worried about Hamlet knowing his fathers death. I rather believe he thinks Hamlet is going to go crazy and kill him due to his current mood of the situation. If he thought Hamlet knew about his fathers death he would most likely of been exterminated by now to keep his mouth shut. He could also be worried about his marriage to Gurtrude because she keeps saying its there hasty marriage that has driven Hamlet mad. This is because if she didn't want to stay married to Cladius he would lose Gertrude and most likely his spot as king.