It sounds like your server is configured to display PHP notices. You should ask your webhost to configure it to log them instead in the PHP error_log file. That is what should be done on a production server. Granted, I should clean up the script a little so it doesn’t create notices at all … which will be done as part of the complete re-write I am working on.
Any way, after they make that change, try importing again because that could fix the 500 error too. If you still get an error, please let me know. We’ll try something else.