Haven't read everything here, so sorry if I'm duplicating anything. But have you looked for a therapist who more specifically works with complex trauma (or might be described as working with childhood trauma or trauma from child abuse)? My therapist says I have complex trauma. I don't know what she puts on insurance papers since that's not in the DSM. I have features of PTSD (diagnosed once after as assault, but did not explain why I was already so self-destructive before that happened) and also some features like an attachment disorder or personality disorder, but not enough to have any one of those official diagnosis as an adult. I am doing treatment for the complex trauma and that makes sense. Everything else was just like whack-a-mole (though important I did some separate treatment for out-of-control symptoms related to eating and addiction).
My therapist is uses body-oriented trauma therapy, several modalities but primarily Somatic Experiencing. If talking doesn't help you much, that's another option. Talk therapy alone did little for me because I only presented my "work" sort of self and thinking and surface selves. Also, there was the intuitive feeling that if I just talked about traumas I would be totally unhinged and wreck myself.
Real trauma therapy has to include a lot of grounding skills, then processing skills. Just talking about it can be retraumatizing for many people if the treatment isn't more multi-faceted, led by a trauma-specialized therapist. That being said, after trusting my therapist (and my own ability to manage), I have shared some info and harder pieces but she also doesn't need details and the form of therapy itself does not hinge on me retelling a whole trauma story. So, there are other options. I have to travel a bit for my therapy, but for me it has been worth it.
You could check the Psychology Today website to look up more therapists in your area, hopefully look for trauma specialization and if you meet with them, bring this up right away (not the details, but that you feel this all connected to the longterm childhood trauma). See what their approach is and you should be able to feel out if they really understand trauma or just want to bullshit around it more. You could also look into Somatic Experiencing, and if that sounds like a possibly helpful route, find a list of practitioners on the SE website. But also helpful if they have worked with complex trauma. Also, if you have not taken MMPI or other assessments to rule out personality disorders, that might be helpful. But sounds more like complex trauma. Anything else would maybe inform the therapy, but also let therapists bill insurance, I suppose. Not sure why they can't diagnose PTSD...probably just you haven't met with someone who understands complex trauma. You have criterion A trauma, and while the re-experiencing part might not be as obvious as with a veteran and response to loud noises, you have that as well as avoidance on the interpersonal level, which is really common.