Look at the exam board and try and work out what they want. Do any of them cite Alport? Assuming they don't then yes you are barking up the wrong tree! Make your Point, show your evidence, give an explanation, develop yours and authors ideas, conclude.
They don't want you to be clever. Just knowledgeable about the text and perhaps it's time period.
To push on to A*, talk about the title and reference the various "mockingbirds" in the story - the dog, tom himself, Boo and the children's innocence (esp Jem). Using the PEE strategy already discussed.