If Torque really wanted to convince the Magister about Brevon, he could have just taken off his disguise to help support his explanation about the alien presence. Was there any reason for him to stay disguised by that point?
A matter of Chaser protocol, perhaps? The only reason Torque revealed himself in the first place was because Carol discovered his secret while he was working in his tent, and told Lilac about this.
Why is it that Lord Brevon decides to organize a convoluted plot involving brainwashing and the manipulation of several forces much weaker than his own army when he could have just gone and stolen the Kingdom Stone himself?
Pragmatism, perhaps. He doesn't know the relative strength of the Avalice forces, and didn't want to run the risk of depleting his forces in an immediate assault. That, or pride. Avalice isn't a worthy conquest, so he doesn't intend to waste troops on it.
After Brevon turns off the oxygen, Milla gives you a bubble shield so you can breathe, but she doesn't have one herself. So how did she survive? And how does a bubble shield help you breathe in a room that's running out of oxygen? Wouldn't that just make you suffocate faster?
Given that Sonic can get a shield with the same functions and both work and exist in unexplained ways, I'd personally just chalk this one up to the magical nature of the shield.
How would a bubble shield make you suffocate faster in a vacuum, anyways?
Playing through the final level as Lilac: Eastern Dragons in myth tend to have 81 scales one of which, the Gekirin, is inverted and serves as a literal Berserk Button that, once pressed, causes the dragon to enter a fit of Unstoppable Rage. After Brevon turned Milla into a monster and forced Lilac to hurt her, Lilac went on a Roaring Rampage of Revenge across the rest of the spaceship and became determined to kill Brevon. That, and the dialogue that took place after both the boss fight with Milla and during the boss fights with Brevon himself, make it clear that he has touched Lilac's Gekirin.
We learn that Milla has been away from her parents for some time and was alone in the wilderness. When asked about it, Milla can only say "it feels like a really long time". Her story intro shows her talking to Mr. Stumpy, an imaginary friend she's carved out of a tree. She seems to be aware that it can't talk back and laughs it off, but the implication is that a little girl has been wandering alone in the wild without any supervision and has become so lonely that she's made something she can talk to just to cope. If that wasn't bad enough, the shooting star and her wanting to make a potion to let her fly into the sky to find them suggests that they're dead or at least missing and she's too innocent to understand, and she's only ten years old!