You should be able to just copy the ebook files from "My Digital Editions" to the NOOK drive.
Using the File Browser.
Once the Nook is already authorized with your ADE ID, which apparently must now be done via the device UI, you don't *need* ADE at all. Obviously, it is much more convenient, but B&N have clearly said "screw that".
As for calibre, why doesn't it work? Do you have the latest version of calibre? Have you posted your problem in the calibre forums?