In regards to Jack's past, he's not exactly very open about it and I DO THINK THE REASON WHY HE GRAVITATED TO JERVIS SO MUCH IS LITERALLY BECAUSE HE REPRESENTS ESCAPISM. Like he adopted the whole Wonderland aesthetic, especially when Jervis gave him the role of the Jack Rabbit, a role that combined both the aspects of the White Rabbit and the March Hare from Alice in Wonderland SO JACK HAS ASPECTS OF BOTH CHARACTERS. He has the White Rabbit's obsession with being "on time" and he has the March Hare's nonsensical madness (like when he's speaking wonderlandian or uses his powers).
But much like Jervis, his trauma seeps through his role. He developed his fixtation on time when his mother first went missing before she was found murdered, nervously looking at the clock that night and staying up, just staring at the clock and counting down the seconds to it. When he got captured and experimented on, keeping the time was the only thing keeping him sane down there after his experiments and he slowly began to memorize the schedule of everyone and everything around him, he knew their individual times and their own personal schedule just by observation alone. It's now become a habit he can't break, even if he tried.
He also becomes more nonsensical and starts speaking "Wonderlandian" when he gets stressed, scared, angry or any other intense negative emotion. He also exhibits rabbit signs of stress like his posture being more hunched, he gets fidgety, tapping his foot nervously and he loses grip of powers which causes the people around him to see strange things that aren't actually there. Basically, JACK IS NOT THE PERSON WHO REMAINS CALM IN A SITUATION AND IS MOST LIKELY TO STRESS PEOPLE OUT.
Jack also isn't very open about his experiences and he doesn't like being reminded of them because it's too terrifying to think about. BASICALLY, HE'S VERY MUCH IN DENIAL AND HE WILL PLAY HIS ROLE THAT HE IS A JACK RABBIT FROM WONDERLAND (whose not actually a character but a role Jervis and Jack made up themselves) WHO ACCIDENTALLY LOST HIS WAY BUT THE KINDLY MAD HATTER HAS HELPED HIM. He only responds to "Jack" and never Jackson or his real full name or even his NATIVE name because if he remembers that, then he remembers his mother and father, and if he remembers his mother and father then he remembers their deaths and then he remembers WHY he "plays" Wonderland and gets overwhelmed, has a panic attack, or even angrily lashes out to convince himself that his WONDERLAND life is the real one and that his real life memories are just bad dreams.
But the more he falls in love with Edison, the more that parts of his genuine self start to show. When Edison opens up to him, Jack just sitting next to him and he's all: "Yeah, I know how it feels when people don't listen to you. When they ignore you because they don't think you matter. No matter how important it is, they'll never listen to you." and Edison just stares up at Jack because he was NOT putting on a voice and Jack catches himself before he smiles warmly: "That's why I'll listen to you when no one else will. I love you." or when Edison is planning a trick, Jack just gets reminded of a random story about the "Great Trickster" from his nation, and Edison smiles BUT NEVER ASKS FURTHER BC THIS IS ONE OF THE MOMENTS WHERE JACK DOESN'T REALIZE HE'S "breaking character" and Edison just appreciating these moments and trying not to draw attention to them so he can get more.
Jack is constantly trying to keep himself stuck in a world of whimsy and wonder but, after falling in love with Edison, he slowly starts to "break character" because life doesn't seem so painful to live as long as he has his Edison.













