Thank you so much for sharing your story on these forums. I'm guessing your age from the '04' in your name, and if this is accurate, this is a really hard time for anyone, let alone someone experiencing the trauma you have.
I think the reality is that not many people your age have experienced serious trauma, and not many will really grasp what you're experiencing on an emotional level, and this makes it hard to feel heard. There are in person support groups for PTSD, depression etc, and I found these really effective and letting me feel heard and understood on an emotional level.
Do you have any sports or other physical exercises you enjoy? Intense exercise is essential for me to manage my mental health. I think this can be a way to push your body out of its comfort level, and force the intense, circuitous thoughts out of your head. You might like something like Parkrun, which is held in most parts of Australia, and should be starting up again soon.
I skate(board) every day now, and that really helps me break out of my head as you have to really focus on your body to avoid falling off! I always wear helmet and (usually) pads though to minimise serious risk. I skate after work, and I find that helps tire me out physically so I sleep better and don't have bad dreams. Avoiding intense or negative TV before bed also helps. I watch Simpsons before bed now.
I notice you've got Harley Quinn as your avatar - have you ever tried roller skating? It's really taking off at the moment. I see lots of women and girls on skates at the skateparks now, of all ability levels, including total beginners. I've seen women come out of the half-pipes doing hand stands, it's amazing.
I think there are lots of strategies for managing internal chaos. Trying to simplify your life as much as possible was a good start for me, i.e. setting strong boundaries with difficult people and minimising any painful relationships.
There are heaps of schools of thought with therapy, but I've found the "Schema Therapy" model really helpful for me. I think it's particularly useful for people with traumatic pasts. There are heaps of resources and "worksheets" online - if you have a psych or counsellor they may be able to guide you. I remember when I was your age I thought these therapy "homework" worksheets were really, really stupid, sometimes even offensive, but you can eventually find an approach that makes sense to you I think. All the best,