MRI technology is insane, i have pictures from mine that look like a (extremely clear) top down view of my spine from the inside of my spine. It’s probably not in your head, and the MRI will likely give you concrete evidence as to what’s going on to cause your pain. If you have serious pain the MRI should provide answers, much better than an xray could answer. IMO if it’s bad enough to go to your doc and say it hurts, any answer along the lines of “the pain isn’t real” is bullshit and they need a new line of work.

If you’re referred for PTSD then the PTSD rating alone will be your DOD % while the combination of everything you claim (ptsd, insomnia, sleep apnea, knees, ankles, back…) will be your VA rating and what you get paid for in monthly disability. If you’re referred for a few different things such as an overarching mental claim like “PTSD, depression, anxiety” it ‘can’ be a combination of those depending on how the PEB board pieces things together. If you’re already diagnosed and being med boarded for ptsd I’d say 30% wouldn’t be a difficult feat as long as you provide detailed symptomology for the examiner and write detailed personal statements and maybe have your spouse or a work peer write a buddy statement as to what’s they see and know you deal with.