Answer and Explanation:
1. The death of Candy's dog portrays the theme that those who show weakness do not have a place in this world and will end up being exterminated in favor of the growth of those who are strong. This death is an omen about Lenin's death, which reinforces even more than within this work, strength is not related to physical strength, but emotional and mental strength.
2. Because besides being old, he is physically "deformed", since he does not have one hand. he fears that this will damage his role at the ranch and that at any moment he will be fired and replaced, without having a place to live and a salary to support himself. If he participates in the George and Lennie Plans, he will also own the doing and will have stability forever.
3. For me Carlson is a cold-blooded man. This is justified by his courage to "get rid" of the dog, which despite being old was a living being, but Carlson showed no remorse in taking his life. However, he respected Candy's decision to kill the dog or not, which shows that he has a certain level of respect for the wishes of others.
4. The struggle between them shows that Curley is based on his superiority and therefore believes that nothing bad will happen to him. This justifies his courage in facing Lennie who is clearly bigger and stronger. Curley's fight is offensive, while Lennie's fight is defensive and shows that he is an insecure character who unconsciously and unintentionally damages people.