@rdflash0788 Hello and welcome! Joining an existing discussion that covers similar questions is a good idea because participating members get notifications of your input. Thank you for your very detailed description of your symptoms. You bring up some great questions.

The symptoms you describe are consistent with cervical spine issues. Surgeons often get focused on what conditions are related to particular levels, and those relate to the specific nerves that exit the spine between vertebrae at the nerve roots. The other type of problem can be spinal cord compression, and it's harder to pin that down specifically as to where symptoms will occur. The 4 mm of listhesis essentially makes the spinal canal smaller when it slides out of alignment. That is a lot of movement. The spinal cord needs to move inside the fluid in the canal when you change your body position or bend your neck or turn your head, and that can make the spinal cord either contact the hard "walls" of the canal or cause some spinal cord compression. That can affect any body parts below that level.

Some of the other issues that can cause similar or overlapping symptoms can also be attributed to a condition like thoracic outlet syndrome. This is something that I have (TOS) along with being a cervical spine surgery patient. TOS causes compression of nerves that travel to the arms in several places in the neck and shoulder area, and if your spine issues were caused by an injury such as a whiplash, there could have been injury to muscles that can cause TOS in addition.

The biggest issue might be the instability at C3/C4 causing the vertebrae slipping and it poses a risk for spinal cord injury. That is something to ask your surgeon about. It may be why they are recommending surgery. My experience is kind of unique in that I had a collapsed C5/C6 disc with bone spurs causing spinal cord compression with 2mm of retrolisthesis (backward slipping). I did not have issues at the nerve roots. My case was confusing to several surgeons because of the somewhat unpredictable nature of where the pain symptoms would be, and they changed location when I changed body positions. I was also working with a physical therapist who would realign my spine resolving symptoms temporarily until it slipped out of alignment again. I had pain go everywhere and also into my legs and feet. I had dizziness and vertigo. The reason that was happening was because my vertebrae were spontaneously rotating with muscle spasms which stretches the vertebral arteries inside the sides of the vertebrae that are part of the blood supply to the brain. All I had to do was look upward at birds flying, and that kinked the stretched arteries causing extreme dizziness and I lost my balance. It also caused intermittent issues emptying the bladder which is a symptom of pressure on the spinal cord.

I found this medical literature with a case similar to mine, and that led to getting help from a surgeon and a C5/C6 fusion that solved all the issues by freeing the spinal cord. I know you have concerns about how many levels would need future surgery. The longer the fused area that you have, the greater the stress above and below that fusion that could lead to more surgery. It sound like you have some tough decisions to make. Getting multiple surgical opinions is probably a good idea because you cannot undo a surgery once it's done. I had 6 opinions. Most missed the diagnosis of why I had my set of symptoms, and one got it right. He got the job.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3111492/
What are your questions now that you have some more information?