Is it possible that CURL isn't installed on the live server? It should be by default, but it appears to not be connecting to the paypal service at all because all of the settings are blank.
Did you log into the paypal sandbox first? I seem to remember that is necessary.
Personally I seldom use the paypal sandbox at all since it is so easy to refund transactions on paypal and the fees are all refunded as well. I'd try in live mode and see if you have better luck.