I couldn't tell you what the next step is. I had to hire a lawyer to get me where I am. It took me 6 years in the appeal process to get my CAPD granted. I had a diagnosis from a VA neurosurgeon but still had to have my lawyer find a doctor to provide a nexus letter.
The VA granted my CAPD in Sept. 2023 as a neurological disorder and just recently more specifically as central nervous system. They initially rated it at 10% but we fought that and I'm still waiting on the VA for their final rating decision.
It sounds like you have what you need from the doctor. Hopefully you are working with a good VSO that can help guide you in next steps. I have a bunch of research that links JP8 and noise exposure to hearing loss. I sent you a message on here if you want it.
Never give up! Good luck.