[Divingduck]

1. Import works for me fine.
2. Maybe because there is something wrong with your subdirectories in 1. or with your system (write protection or AV?).
3. Correcting metadata in calibre do not automaticly change the metadata in a pook. It only change the metadata record for the library. It is not wanted to change the book automatically as there a serious necessities not to change original documents in a library. If you send a book to a device the metadata for this copy will be update to the actual data you have update in the library. In case you have the necessity to update the files within the library, there is a internal plugin that you can use manually for selected books.

Polish books and Embed metadata. Both are available in calibre. For using you need to make them visible via Preferences -->Interface -->Toolbars. Select e.g. Main toolbar and look to the left window for the action Polish books and/or Embed metadata. Copy them with the green arrows between the windows to the right window for current actions and move them to a position you like to see this actions. A third way is the external Plugin Modify ePup (vial Preferences get new plugins).