What are some things that seem factual about Boo Radley from Chapters 1-6 of Lee's To Kill a Mockingbird?

When the children hear the "neighborhood legend" and talk with Miss Maudie, they learn some facts about Boo Radley. 
Since there must be a reason why Boo never comes out of the house, the children believe that he must have done something when he was younger.
Chapter 1
Supposedly Arthur ran around with with the Old Sarum boys and they all created a disturbance around the town square. They were apprehended by the town beadle and later charged with disorderly conduct, disturbing the peace, assault and battery, and using abusive and profane language.
The judge decided to send them to the state industrial school, which was actually the best secondary school in the state. But, Mr. Radley did not want Arthur to go there, so he promised if Arthur were released to him, there would be no further trouble. Arthur was not seen for fifteen years.
Once Mrs. Radley ran screaming into the street, shouting that Arthur was going to kill them all. Thirty-three years old at the time, Boo was locked in the basement of the courthouse because the sheriff did not want to put him in the jail with offenders. When Mr. Radley did not come for Arthur, men of the town told him Arthur would die of the mold if he did not retrieve him.
Chapter 5
Miss Maudie tells the children some truths about Arthur Radley: she relates how polite he was as a boy, and how stringent his father is.
When Atticus spots Jem dangling a line in front of the Radley window, he becomes furious and tells them to never bother the Radleys.

"You stop this nonsense right now, every one of you." 

Chapter 6
When the children decide to peek into the Radley window, there is a shotgun blast made by Boo's brother, Mr. Nathan Radley. Jem is so terrified that when his pants catch on the barbed wire, he struggles out of them. 
Knowing that Mr. Nathan will check to see what damage they have done on his porch, he will then notice the pants.
Later, Jem decides he must go back and retrieve his pants. As he approaches the porch, Scout watches and listens. Finally Jem returns, pants in tow.