Based on this excerpt, the narrator makes the assumption that his mother would much suffer if she knew the messages referred in here, so the best option for the assumption is the second one "that the messages would increase his mother’s suffering" because the son wants to protect his mother from any suffering, which makes the connotation that he loves her so much not letting anything hurt her as one of his main concerns. Additionally, the members of the Radio Shack are not mentioned in the passage, then the last option cannot be eligible; the father's emergency money is involved, but it is not specified what the son will do with such money at the Radio Shack; and the mother would understand the messages but would get hurt too, that is why her son wants to protect her.