Honestly, you just need to think about who your character was and how they became the person they are at the start of the campaign. You've done this all that you would need to to justify your characters class and race, but you haven't done it at a level that helps you understand who your character is and why he does the things that he does.
If you start asking questions about who your character is you'll usually be able to find the themes and contradictions that make them interesting and work down from there to find interesting quirks and personality traits. I came up with some (probably too many) questions to try and figure out who your character is at his core, but that's easier for someone who doesn't know your character. You can try to answer these if they match who you feel your character is, but if they don't you might need to try to divorce yourself from your understanding of who your character is as if you don't know them at all. (Which at this point it seems like you don't really all that much anyway, so what's the worst that could happen? ¯\_(ツ)_/¯ )
Who was your character growing up? Was it decided that he would join the Lord's Alliance earlier in his life or only recently? Did he make this decision? "Doing good and protecting the weak" isn't necessarily a bad ambition, but it is a pretty lofty one. What kind of life does he lead that he can worry about that over his own survival or the survival of his family/people he cares about? Does he have people like that in his life? He's in the Lord's Alliance, but is he an agent or a lord? If he's an agent, then who is he loyal to in the Alliance that he serves under. If he's a lord then why does he choose to do his work himself? From what I just now read about it, the alliance doesn't seem like the type of organization that does good things and protects the weak for the sake of doing them, but more a coalition that benefits from it's members helping each other to sustain their own interests. If that's the case in your campaign then why was it your characters best option for doing what he wants to do? Was it previous loyalties that made it only/best the route he could take, or is the Alliance the best way to achieve his goals (from his perspective)? If it's loyalties, then how does this affect his upbringing? Is he a knight in service of a lord or a member of a lords family who would be too far down the succession (or ineligible for whatever mechanism is used to transfer power), but still loyal enough to act as one of their agents? Maybe he is eligible and is being groomed to replace a lord in the alliance through his service. Maybe he's not a part of a lord's family and proved his loyalty through hard work and dedication, or through keeping a few secrets.
I came up with all of these by just reading what you wrote and looking at a 3 paragraph long description of the lord's alliance. It's way easier if you don't come at it thinking you know who your character is.
tl;dr: Ask questions about how your character became who he is and what contradictions that creates in him. Those are what makes him interesting and his personality and quirks will come from them naturally. Don't try to make him perfectly good and pure, it will only hold you back.