1. You can save your already finished label files (*.aud) somewhere else, and then copy them back after changing operating systems. Also, uninstalling AudioLabel does not delete any of your saved label files.
2. Error 1680 has to do with your saved print driver settings. It sounds like thing were changed when you upgraded to Windows 8.1. To reset the print driver settings, please uninstall AudioLabel (very important), and then download and install a new copy of AudioLabel.
Before reverting back to Windows 8.0, first make sure you can print from other programs using Windows 8.1.
If you can print from other programs using Windows 8.1, then AudioLabel should also work. You might just need to uninstall and re-install AudioLabel.
Please let me know how it goes.