[Gnomasz]

1. Yes, I don't see why not. Nothing in the description excludes any type of command, and for 35 points it should be powerful. Regarding important, but small details, though, I'd maybe make the party roll Interrogation at +4 to be able to ask the right questions.
2. I think I'd make an IQ roll for the victim, probably at a penalty, and if they pass, let them slip with an answer like "only if you tell me to, master". Also, quite often the answer would be "I don't know, depends on the situation".
3. I'd cling to the word "principles". That is something more than "my well-being", so I wouldn't give the Evil Wizard no Quick Contest, unless he were all "never share any knowledge with anyone" – which should mean weaker, uninformed sidekicks. Besides, if the PCs manage to capture the wizard and overcome his Will, they deserve the info. The merchant would get a roll if he were greedy. The "significant tactical advantage" would only trigger QC for someone extremely loyal (or fanatical) or always secretive (the type that wouldn't talk about job with significant other, not to tell any details).
4. I'd say yes, but if your commands become contradictory, I'd give the victim a new QC.
5. Yes, but the victim would know what's coming the next time and could try to run (or attack, or cover ears).