Answer:
1. He just killed his best friend, so he's understandably depressed.
2. Even though he knows he made the correct choice; he still finds himself angry at himself. He's uncertain and debating his decisions.
3. George is content since he is confident that Lennie is also content and safe.
Step-by-step explanation:
This is just my own opinion. Of course, you are free to alter it to your own.