No, you don't have your details correct.
Yes, ATV firewall is running by default, but (more importantly) it sets NO rules denying traffic from anywhere (its open to any/all traffic, in other words)...
Hmm. The first step to get ssh working is disabling the firewall.
http://tutorialninjas.net/2007/03/26/hacking-the-apple-tv/
"Vectors" as heard on Star Trek? What are talking about? Speak in "real" terms that have "real" meaning in the technical world, please.
http://cybercoyote.org/security/vectors.shtml
http://en.wikipedia.org/wiki/Vector_(computing)
With a closed platform there are less points where a virus/worm could get an entry point into the system. Vector is the "real" usage in computer viruses/worms.
One port? Do you understand anything about tcp/ip networking?
One ETHERNET PORT... you seem to jump to an awful number of conclusions.