Why not have the LLM copyedit it, too?
AI's don't like working with really large amounts of text. They will not go through a text linr by line and analyze it, not without having a highly specialised "AI" or harness or whatever you call it.
If you simply ask it to remove ending paragraphs like that one in the OP, it will write a script that tries to find phrases like "if you want" and then check the result of the script and replace those. It will NOT read the whole book line by line to find instances like that.