Q 1: Pulled from your list. He's not an extra model. You'll lose the model, and gain a traitor IC*.
You will not lose the special abilities of the squad (e.g. an extra heavy weapon for having 10 models, or the ability to combat squad for space marines).
Q 2: Yes. But it gains the profile in the list, so the deff dredd, if you have one as a troops choice, would no longer be a deff dread, he'd be treated as an independant character to a troops choice with the profile listed in the mission.
Q 3: Yes, the stat line replaces the model's special rules. He loses his profile and wargear and gains the wargear and statline in the mission special rules.
Q 4: I don't know the answer to that.
*It does say he gains the "independent" special rule, which I take to mean he gains the independent character special rule, but it also says he can "join any troop choice in your army..." which, is different than the IC special rule.
I know I'm not the TO, but I'm pretty positive my answers are correct. I'm not saying the missions are well written, but the traitor is pretty clear. With the exception of the "independent" and restriction to joining troops paradox.
I suspect the 'Ard Boyz packets will be a little different than the sample missions posted. These were likely a rush job to get them out for practice games. At least I hope so as those are pretty terrible as far as copy editing goes.
I do think this is a good idea for a thread.
I have a question regarding the DoW mission, because of the deployment type do we night fight on turn one? So that all missions have a turn of night fighting?