We have added clarifying instructions.
1. Yes, if it is a child you can infer their surname from the parent's surname. "When the surname of the primary person is not present, the surname may be determined by looking at the surname of either a parent or spouse."
2. We only need line numbers keyed for the records with 2 pages and those are listed horizontally. "Line number should only be keyed on images with horizontal lines printed on the page to separate records."