The medical process can be frustrating! While I can’t relate to your particular medical issue, I do have a special issuance medical. The entire process took me about 4 months for my initial 1st class SI.
As my original ATP class was quickly approaching and I had exhausted other means of getting status, I enlisted the help of my US congressman. His office made an inquiry to the FAA. Perhaps it was coincidence, but about two weeks later the FAA was calling me asking where I’d like my medical faxed. Yes, you read that correctly. The FAA called me.
Others have suggested to never take this approach because perhaps it could backfire (and cause the FAA to drag their feet). When asked, these people did not go through the process so I’m not sure what evidence they had. I did go through the process and it worked for me. It has not backfired at all.
My condition is one that the AME can issue (after the initial medical is issued) as long as my medical condition does not deteriorate. I have renewed it once and my standing approval for this was good for four years (if I remember correctly). If your medical is approved, the FAA will send you very specific instructions on what you need to do (example: bring certain documentation to subsequent exams). Follow those directions exactly and the process will go much smoother.
I am currently in initial training for a 135 commuter operation. In my class of 10 people, 2 admitted to having special issuances (including me). I can’t speak to 121 operations.
Best of luck to you! Hang in there!!