Remove Books from iCloud

I opened Books on my Mac to add a new PDF to it, and it started syncing items to iCloud (I have a hundred some book documents the Books app on my Mac). But my iCloud is almost full and half the collection couldn't sync. Actually I DON'T want the books synced to iCloud. I just want them to stay on my Mac.

I haven't purchased any books from Apple. These are just my PDFs and other books files that I'd like to have collected in the Books app on my Mac.

As some other threads have pointed out, I went to System Settings > Apple ID > iCloud > iCloud Drive > Apps Syncing to iCloud Drive: Options and unchecked the box next to Books. If I check this, Books just keeps uploading more books to iCloud.

In Books, I've unchecked both boxes in Preferences/Syncing: Reading Now and Collections, Bookmarks, and Highlights.

I can see in iCloud > Manage there are still 1.1 GB of Books data in my iCloud.

How do I get rid of all that data in iCloud?

I want my iClould books data all cleared out. I want to keep my books on my Mac.

I will not buy any more iCloud space from Apple. I don't need or want it.

I have seen various similar threads but can't find any solution to this and I cannot get other work done since iCloud is full.

This is on top of a lot of other current frustrations with Apple, on whom I am entirely dependent. I am so frustrated. So I would really appreciate any help. Please.