1) [edited, I was wrong]
2) Sorry, I didn't understand. Status effects won't have any effect on someone you gave CM to (unless lots of them occur at the same time), if this is what you meant.
3) In a team of 7, casting it to all teammates can be tedious. It is used mostly as a status effect breaker. However, you can cast it on your defenders, blasters and controllers friends ; they haven't any status protection.
Scrappers and tanks have their own status protection, which is enough to handle 3 (for scrappers) and 4 (for tankers) at the same time. On large teams against some factions with many status effects (maltas, tsoo, carnies), you might need to CM tankers and scrappers.
1) Duration 90 seconds, recharge 4 seconds, animation time suckky...
2) Yes it has a preventative effect so dropping it on your group before a fight is useful and it has a minimal and undocumented stacking effect according to some of the US forums, so having two Empaths drop it on one person may help.
3 It really depends on the team you can keep it perma on all 7 teammates but you'll be doing very little else the smaller the team the easier it gets, the best advice I can give is figure out which teamates need it most (e.g. blappers) and which opponents require it (e.g. CoT). As a rule of thumb I drop it on people if theres time before a fight if I know we're facing a mezz heavy mob and that my team knows to give me a CM or ZZZzzzZZ when they're stunned.
Oh and it's the bane of any Stalker in PvP 
I picked up CM this week and i have some questions about it:
1) Wich is the duration of the CM effects ?
2) Has CM even a preventive protection from attacks ?
3) Wich is the best tactics using CM ? Casting it often to all team8s ? or only in case of immob. sleep. etc ?
In 2nd case is there a chance to know who needs CM (without seeing the animations of imm. sleep. etc ?)
thanks a lot