ad 1) Yes. Full version supports multiple websites.
ad 2) Try to replace file
app/code/local/Artio/MTurbo/Model/Mturbo/File.php with file in attachments. There is removed checking of no-route title.
ad 3) You have to enter the download id. If you see your name the download id is ok, and you can upgrade to full version by pushing the orange button "Upgrade to full version" in the header. Don't forget refresh cache, please? If you would not work then probably your web server has no permission to write on disk. In this case contact us we send you package for manual upgrade.