OK, first, calm down.
All web traffic on NTL goes through an NTL proxy server. The securitymetrics.com portscan is incorrectly testing the NTL proxy server, not your PC. Try a different scanner like
https://grc.com/x/ne.dll?bh0bkyd2
Now, that being said, I wouldn't worry to much about "stealth" vs. "Closed". In both cases, your computer is not accepting connections on that port and there is nothing anyone can do to your computer if its not listening.
Some people will say "stealth" is better because people won't be able to tell that a PC is even there, but they're wrong. So, don't worry too much about it eaither way.