Is there a doctor in the Pensacola area that can provide a DBQ and nexus letter for lower back and mental health condition?
I don't refer to anyone there. However, the good news is that you don't want or need someone in your region to do a DBQ or an IMO for you. You don't need to meet the doctor face to face, all this can be managed over the phone and in emails. The doctors can write up what you need based on medical records that you provide.
You can find your doctor here. These are the small handful of people I trust to help you take care of your claim.
I have to warn you that the doctors who write IMOs for mental health exams probably aren't going to feel comfortable writing a DBQ/IMO for your back and docs who work with physical issues won't write the mental health portion you need. You can talk with any or all of them for free so you'll get some good words of advice while you decide. Good luck.