"per se evidence of unease" and distress are different. Someone can feel uneasy about their looks/identity and not be in distress. Stop trying to generalize the whole community.
You are talking about degree of the same basic sensation or perception. The afflicted can articulate a difference in their mind between how they feel, or, in other words, "what they know is their gender identity," vs their biological sex, and they have a strong enough negative emotional response to warrant taking action to do something about it (whether that is actual treatment or just seeking affirmation from support structures or just saying you are going to wear a dress and be happy). The flip side of this coin is those who report no negative emotional response to abiding by their biological sex, but feeling an increased POSITIVE emotional response from adopting a new gender identity. This is the same thing, basically.
Both of these are the brain giving feedback - either outright negative feedback to reality, or positive feedback to fantasy.
Let's try a different scenario. Say you were raped as a kid. If you experienced no long lasting negative effects from it, would you be classified as mentally ill? No, you would be a rape victim.
But a rape victim can point to something external that factually occurred to them.
No one is trans without having a brain that doesn't match their biological reality.
Whether they are heavily suffering "distress," or "unease" or merely driven to select a different identity, the fact that they are choosing an identity that is different than their biological sex is per se evidence of their unease with their biology, ie, their reality.
Now lets say you have all kinds of symptoms related to that trauma. We don't label you as mentally ill because you were raped. You have the label because you have PTSD based on the symptoms associated with the event. That is the same with trans and gender dysphoria. It's the symptoms related to the feeling of being in the wrong body that create the mental illness, not the thought of being in the wrong body itself.
Yes but again, the impetus to identify as trans only occurs with the dysphoria or disconnection from reality that one feels to begin with, not as a result of something that happened to them in nature.