Peter is writing about characters in Wonder by R. J. Palacio. But somehow Jack Will got that I had smiled at him. And he smiled back.

"Julian's not a nice person," he whispered before Julian and Charlotte reached us. "But, dude, you're gonna have to talk." He said this seriously, like he was trying to help me.

Which best shows that Peter has made a personal connection that helps him understand Jack Will’s character?

Jack Will is very impatient with Julian. I think Julian has been a bully to him before, and that is why he warns August to speak up.
It is not a good idea to speak up to Julian. Jack Will should not have told August to talk. Talking will get Julian mad, and, later in the story, August will be sorry that he bothered Julian.
I think August and Jack Will should learn karate to defend themselves. That is what worked for me. Now, no one at school ever bothers me. I love competing in karate competitions, too.
At first, Jack Will seems bored with August and the school tour. But at the end of the chapter, he tries to help August. I understand how this happens, because my best friend and I did not get along when we first met.