1. It's been on for a while now. It's currently in its second (and thanks to Nick, final) season.
2. Not sure on that one. Considering Nick only aired HALF of the latest episode, I guess it will have to end in a ".5"
3. Because, basically, Nick sucks. They gotta make sure that their Rugrats, Rocket Power, & Butt Ugly Martians get their 75% of the air time, so that leaves Zim playing Musical Timeslot with the other shows.
Careful what you say in regarding Zim coming to CN.. .that topic has been beaten like a dead horse on TOO many occasions. It would be nice, but considering that Nick holds on to its cancelled shows with a death grip, don't expect to see it anywhere else for a LONG time (if ever.)