I can do one here but you will have to ask about each character separately.
The mockingbird symbolizes grace and kindness that is easily hurt by a very unforgiving and often cruel society. Certainly Tom Robinson fits this motif. He only tried to help Mayella Ewell but was punished for it.
"'Mockingbirds don't do one thing but make music for us to enjoy. They don't eat up people's gardens, don't nest in corncribs, they don't do one thing but sing their hearts out for us. That's why it's a sin to kill a mockingbird.'" Chapter 10
"There's a black boy dead for no reason".... Heck Tate Chapter 30
“I said somethin‘ like, why Miss Mayella, that’s right smart o’you to treat ’em. (Chapter 19)
“Yes, suh. I felt right sorry for her, she seemed to try more’n the rest of ‘em—”
(Chapter 19)
The way that man called him (Tom Robinson) ‘boy’ all the time an‘ sneered at
him, an’ looked around at the jury every time he answered—” (Chapter 19)