Facts established by Mayella Ewell's testimony?

Mayella offered Tom a nickel to break up the chiffarobe.

Mayella lies when she says that this is the first time Tom has helped her.

Tom couldn't have beaten Mayella because his left arm is twelve inches shorter than his right, due to an accident in his youth when the arm got stuck a cotton gin. Mayella's injuries prove that she was hit by someone who was left-handed.