To Kill A Mockingbird: Chapters 15-16

Chapter 15: On page 146 the fourth paragraph in happened to confuse me very much... I had no clue what was happening in that exact paragraph. What are the kids doing downtown? What do those men want from Atticus? Who is Heck Tate? What are those men and Atticus talking about? It seems a little creepy. It said when Scout dashed over with Jem and Dill running behind, fear flashed through his eyes. Was it fear for the children; that they were going to get hurt in some way? Or is it something else? I thought it nice that Scout stood up for Jem like that and hurt an older man just to protect him even though she is 4 years younger than him. On page 154 when Scout is rambling and starts talking about entailment, I'm not positive she really knows what she's talking about or is just repeating something she heard an adult say once.
Chapter 16: I find it very sweet how Jem let Scout sleep with him for the night since she kept on having frightening flashbacks of that night. I find it interesting how on the bottom of page 157 Scout talks about how she hopes Jem understands older folk when he gets older like she already does. But then to prove that wrong, she says that she wouldn't when she gets older when really, she would because everyone starts to understand at a certain age. I believe this could be an example of unreliable narraration maybe? Is there a reason in the book why Jem is telling Dill of everybody in Maycomb?pg. 159