after mrs. joe gets attacked, why does pip believe that he is a suspect in the crime? why does he worry that he provided the weapon for the attack on her?

Pip feels that he will be implicated in the attack on Mrs Joe as the weapon that was used was an old leg-iron. Pip believes that it is the leg-iron that the convict on the marshes removed when Pip gave him Joe's file, and the food. He still harbours guilt for the theft of these items and for helping a convict, and these worries are compunded by the possibility that his actions led to Mrs Joe's attack.