Hi Richard,
1. Ok, we have fixed this issue, please see:
Fix 4 for FileUltimate v2.12. We are currently working on a new version which will feature streaming the file directly to the user during "Download as Zip" action so the user will not have to wait for the temporary zip file to be created.
4. You can change the related message (string key "314") in the language file. The resource files like language files are supplied in the original download package (Resources subfolder). Please see the readme.txt file for more details on customizing the resource files.