[Sabardeyn]

jhs,
The really short answer, for all your questions: You can't.

Calibre needs a certain mandatory file structure in order to be able to automate some of the processes which it has become famous for. So calibre uses an ../AuthorName/BookName/booktitle - authorname.ext structure.

Which means you always need an author. Even if it's only a dummy name, you must have an author. Because no operating system will allow you to create a folder called null/non-existent within which you would need to place the book.

The book name is based on whatever is entered into the database so you can control that with one exception: total path length cannot exceed about 250 characters. Once you get into that range, calibre will start to truncate things. Note that this is a Windows (any version that runs the FAT or NFS file systems) limitation. Other OSes do not have this inherent limitation so their path and filenames may not be truncated.

For what it's worth, you will find after some time using calibre, that you really don't need to muck about in the library directly. It's kind of like a bank vault, keeping your ebooks secure. Whenever you want to read a book, calibre will send a copy to your device. Besides using the ebook files directly, whether manually or through some other program, is likely to cause damage to the file structure and the calibre database eventually.