1) The increased signal within the bone marrow simply means that the marrow is being lost due to degenerative changes
2) AP diameter is the distance from the front to the back of the spinal canal
3)All of your symptoms are not explained by your spinal problem. I would recommend seeing a neurologist who can help you sort through these problems. Without seeing you I could not recommend a specific treatment.
Good luck
Regarding the pain medication, what they have prescribed for you is for mild pain, I believe you can even buy this over the counter in the form of Aleve. If your pain isn't being relieved, you may need a narcotic which you will need to request. If the doctors won't prescribe it then you can buy it legally online but you will need to fax your medical records to the online physician who will call in a stronger prescription for you, and usually with a couple refills. Good luck to you and I wish you well. -CM