OP please take comfort knowing that the actual people who will be rendering an admissions decision at Brown won’t be focused on one element or score in isolation, comparing you to averages and will be paying attention to details. The Brown admissions staff will evaluate your application holistically and juxtaposed not just against other students and stats but relative to what you specifically could bring to the Brown community and conversely how the Brown experience could benefit you.
Given your focus on writing your essays will likely be important not just in the story they tell but how it is told. Additionally the lack of APs at your school will likely center some attention on LORs so that your relative performance amongst peers in the eyes of teachers will be of interest.
Once again almost impossible for anyone without that perspective to meaningfully chance you. Hang in there you have achieved a lot!