Why didn't Virginia call the police after she trapped the trolls in the elevator or after Wolf attempted to eat her grandmother?
Because both of those situations were way too crazy for the police to believe?
Not really, they're basically just a flamboyant serial killer and a weird looking street gang as far as she knows at that point.
She knows the dog can understand human speech, so she's probably taken the trolls at their word that they are trolls. If she called the police about them, or Wolf, she'd be asked a lot of questions and probably start babbling about intelligent dogs and look crazy. She's spooked, she's not in the clearest frame of mind.
Why does Prince Wendell's voice sound muffled when he's holding a pencil in his mouth? He speaks via telepathy, if that.
It's not telepathy, it's magical translation of Dog to English.
Why is it the key Tony got the Tooth Fairy to make didn't work on the door? I can see three explanations:
It was the wrong key.
The watch Tony gave the Tooth Fairy was in fact fake (lampshaded by him having doubted its authenticity himself as a Call-Forward to this moment), so the Tooth Fairy retaliated by making a faulty key.
There was a prong or other shape to push aside tumblers on the other side of the key which didn't get reproduced, since the impression in the soap was only for one side. (See Indiana Jones and Toht only having one side of the medallion burned in his palm.)
What happened when Wolf gave his will to the Queen? She gave him a very intense stare and it appeared to be magically binding, but afterwards he seemed to have the power to disobey her when he wanted to. Was it magic, or just a regular promise to serve her?
From the point he meets Virginia onward, he isn't "able to disobey whenever he wants" so much as constantly fighting/resisting her. The implication is either that True Love could undo her compulsion/binding or that Wolf was very strong-willed and could break free once he had something/someone else to believe in.
Was there some kind of romance between the Huntsman and the Queen? In his first scene, he kisses her hand and she presses it to her cheek, but it's never hinted at again.
Entirely possible. The fact she is so powerful would make her the strongest predator of all other than himself in his eyes, and therefore probably the only one worthy of such a thing. On the other hand it could just be a sign of medieval fealty/villainous devotion.
Seriously, what the goddamn hell were the writers thinking with the Gypsy subplot? Colorful magic stereotypes are one thing, but the warnings Wolf gives Virginia and her father are straight out of the Middle Ages and Nazi Germany. Gypsies aren't even relevant to the famous (to Westerners) fairy tales this series revolves around. It would be comparable to "What Makes the Red Man Red", except that "Tenth Kingdom" was made after the turn of the century.
The writer, Simon Moore, is British, so he would at least be more aware of (and even possibly influenced by) such stereotypes than American viewers. Why he would think it appropriate to include them is another matter. On some level they are clearly there to add more complexity to Wolf by making him a hypocrite (and showing the oppressed can still be racist too), but their portrayal and plot goes beyond this once the curse is included—which is ironic, since before that the whole scene with Wolf, the Gypsy Queen, and her grandson completely proved Wolf's prejudice wrong, and the Gypsies' previous attitude as either well-justified suspicions of strangers or a Secret Test of Character. If Moore had just stopped there... They also exist to provide prophetic hints for Wolf and Because Destiny Says So for Virginia, but those could easily have been included another way and are themselves another stereotype (albeit one based to some extent on reality).