What event affected Mr. White's personality and behavior?

Belief in the paw undoubtedly shaped Mr. White's behavior. 

In the beginning of the story, Mr. White takes a chance and makes a wish.  At the bidding of his son, who is skeptical about the paw, Mr. White asks for two hundred pounds, which is what he needs to pay off his house.  After the does this, he thinks that the paw moves.  He begins to be afraid.  Later that night, he thinks he sees...

Belief in the paw undoubtedly shaped Mr. White's behavior. 

In the beginning of the story, Mr. White takes a chance and makes a wish.  At the bidding of his son, who is skeptical about the paw, Mr. White asks for two hundred pounds, which is what he needs to pay off his house.  After the does this, he thinks that the paw moves.  He begins to be afraid.  Later that night, he thinks he sees a monkey's face in the fire.  He ignores these events and goes to bed.  A few days later, he gets a visit from Herbert's employers, and they say that Herbert died in an accident.  The employers also give two hundred pounds. Mr. White begins to believe that the paw did this.  Later at the bidding of his wife, he wishes for this son to be alive. 

After he does this, he hears a knock on the door.  He knows it is Herbert.  In a panic he wishes that it goes away.  

In light of these events, Mr. White is a changed man.  He believes in the power of the paw.  He realizes that he cannot tamper with fate.  This is exactly what Sergeant Major Morris said in the beginning of the story.

An old fakir put a spell on it. He was a very holy man and he wanted to show that fate ruled people’s lives, and that to interfere with fate only caused deep sadness.