So Brown has the PLME program which you might as well try for. In your case, if you have worked with people at Brown and can name drop a few as well as getting rec letters, you may have a better chance than most people.
IMO: reaches are reach because the percentage of people getting accepted is so low. You can’t just say you want to go and expect to actually get in. This is for any school with sub-10% acceptance rate. But if you see the accepted posts, the same kids get into many of the same schools. The quality of applicants matter.
Reading your original post, I would personally suggest rearranging your ECs. EMT and writing a children’s book caught my eye, whereas the non-profits made them roll. I think non-profits are overly done and very cliche, no matter how genuine your organization is.
Your research experience will also help. But it’s best coming from your mentors in ways of rec letters and not you writing them yourself on an application. You can submit your published article to show what you have done and let the AO decide on the merit themselves.
For sure you are a strong candidate and will do well. Just none of us here can tell you where you will end up, but I would be curious to know next year of all the places you will get accepted.