1). Insanity is an interest character trait but only when it is applied consistently across the character. So make clear how Maestema's psychosis makes him manipulative or is amused by death but still wants to be a doctor. Also think about lesser ways this could be tied into the character such as having a particularly dark sense of humour or spending his spare time learning about anatomy or whatever.
-edited the personality.
2). Two things about the semblance; could you at least in general terms discuss how much stronger Maestema is getting and secondly clarify how Grimm interact with the 'negative emotion' thing. Although it is clear that Grimm themselves are attracted to negative emotion, they themselves might not be capable of feeling at all.
-stated how much stronger the strength gain per negative emotion.
3). Regeneration seems to something you have quite an attachment to and although I would pretend to understand it I do want to point out an issue you might not have thought about. All fights with students will be to aura break at worse meaning that even if Maestema only has 10% less aura than everyone one else that is a significant disadvantage. And the bonus you get in return is not really that powerful as it would only work in missions and even then your team has to be in pretty bad shape to need it. I'm not saying everything has to be optimised just making sure you understand the consequences of your actions.
-yeah.. I understand the consequences and willing to take the risks