After associating cursor files to RW Cursor Editor, I can't preview or directly apply cursors. I tried repairing both and uninstalling and reinstalling the installer.
Did you associate the files from Windows or from the editor? If from Windows, you'll likely have to dive into registry to fix it (namely deleting everything under HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Explorer\FileExts\.cur and HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Explorer\FileExts\.ani and then disabling and enabling associations within the editor).
If you used Change Cursor and it stopped working, this is natural - you'll just need to re-install it to reactivate the functionality each time you change the associations.
Can I associate the file to both, or at very least have the preview?
Yes, first fix the preview as I said above and then you can re-install Change Cursor.
The right-click still doesn't work, after un/reinstalling.