I can’t help you with direct advice or information on book publishing, or literary agents.
I know little about the world of book publishing but I do know that if you want a big-name publisher, you MUST come through an agent. My sister-in-law, Helen Townsend has written over 30 books. Read her fantastic Guide to Publishing Your First Book
I’m an expert only in journalism.
The skills needed in journalism and writing books overlap . . . but journalism and book publishing are in fact worlds apart.
J K Rowling, the world’s richest writer, was knocked back 17 times before one publisher saw her genius in the Harry Potter books.