The difference between a summary and a main idea is length. They both provide only the important details from the text, but the main idea sums up the text in a single sentence. Therefore, a main idea is defined as a single-sentence summary.
The main idea is what the book is mostly about. The theme is the message, lesson, or moral of a book. Summary is a brief statement or account of the main points of something.
In order to determine the author's perspective, you need to figure out what opinion or attitude the author has about the subject and that alone can sometimes be tricky.
