I often wonder if I'm a 4w3 core who got traumatized into being a core 9. Like when I was younger, I didn't really fear conflict much, in fact I started it quite a lot. I wasn't scared of disappointing others, or to shake things up, as long as it meant getting what I want. Suppressing anger? Feel the heat. I wasn't even an optimist either, my only real optimism was the 7ish kind of liking to try something new. Then when my mom died and my life got better and I started realizing what a little twit I was, as well as being manipulated by others into being submissive, that's when I really started acting 9ish. When I started swallowing my anger, when conflict became frightening, when getting what I want was too much of a fuss. One of the reasons why I'm still not truly comfortable with 9 as a typing-pretty comfortable but I feel like if I didn't go through those sorts of things then my 4w3 would be at the center, and it's still a very strong force in my life but now my 4 and 9 are competing. When I was younger I wouldn't question if having no identity was my biggest fear or not, because I feared that long before I feared any of the 9 fears. But now, some days having no identity sounds the most scary and then other days the fear of separation sounds scarier. What if I had a therapist who "cured" me of my meekness and I became a full throttle 4 again? And I do think I go to 2 under stress....
I ran into a similar issue, recognizing myself as 9 was very difficult because as a child I was much more moralistic and even aggressive (honestly I think if I hadn't experienced trauma, I'd probably have been a 1w2 or 5w6/6w5 core and maybe so/sx considering how I was described in my youth). Realistically, looking at how human development works, "identity," primarily temperament and such is considered to be formed by 10 (give or take, considering when the upper limit of identity fracturing disorders are formed) and that identity is cultivated and developed through experience afterwards, with the largest parts of growing development being when you reach adulthood (at least at a biological standpoint, between 20-26 you hit the end of your "growth" at a neurological level give or take). Of course you can progress afterwards, but between 10 and then after the basic identity is defined, your major fears, interests, and personality traits are formed (I'm not ignoring the fluidity of personality after this but like... Neurologically speaking
if I'm not mistaken major personality development outside of trauma related change is much more difficult and typically less dramatic because you've defined your core traits). This is a big reason people don't recommend typing yourself till you hit your 20s. A lot of people have pretty drastic personality shifts between like 12 and 17, so the fact that the younger you is far different than the current you is not shocking (although I'm sorry you had to go through terrible experiences that make you feel as if you did loose what you potentially could have become).
Personally, I can relate a lot to disintegration to 7 and integration to 8 a lot; In part, I think it's because it does look kind of like my inta/disintegration paths already (ie. disintegration to 6 is still disintegration to a head type and gives me a lot of that mental, frantic energy; 8 and 3 integration are both about being more apt to engage with your impulses and assert your presence), but my 5 fix is quite prominent as well and competes with my 9 in a sense. Observing you (not to have a bias; I do think you are a 9 core as well, though I don't know you on a personal level, but especially my ending paragraph is not directed at you specifically), I think you could potentially run into the same problem with having a strong secondary fix with inta/disintegration lines that resemble their fix (ie. 6 and 2 are both compliant types which in unhealthy ways can be very vocal and attention seeking, 3 and 1 are both types which in health can be incredibly self realized, assertive, and strong in what they want and believe in).
The positive outlook triad as well also gets a bad/innacurate rap, especially by those who become fixated on the "positive" aspect of that. The positive outlook triad is not that related to optimism and, especially combined with more exploratory types (ie. 4 and 5), are not even always evasive of heavy topics, especially those that aren't directly related to the self. I love gore, most of the stories I write are absolutely miserable and because I like to explore miserable subjects (but of course, I don't have a 4 fix, so I still avoid a lot of my emotions and especially initially was inclined to type as types which fit my ideal self, ie 5 and 6 and even 1). I can't even begin to tell you how many 9 cores I've come across who have identified as pessimists and have been strongly contemplative. Especially holding in emotion will leave the internal realm incredibly frustrated, heated, and critical, and shameful (but often in a way that specifically deviates from the heart triad version of shame).