You gave us a lot of information, and you asked for a lot of information! So the final diagnosis is polyneuropathy? Are they certain you cleared that infection? Are you on any medications? There are medications that can lessen nerve pain. There are also implantable devices that are sort of like pacemakers, but they electrically stimulate your spine and/or spinal nerve which can make a big difference.
There are implantable pumps that administer small amounts of pain medication or muscle relaxing medication into your spin at a steady rate which can really help. Those both require a small surgery, and are usually for people with intractable pain or spasming.
Are you having weakness and dysfunction? Are you able to walk properly and get through the day? What is your biggest problem at this time? Clearly your problem isn't just lumbar/sacral spine if you are having problems with your hands as well. Let's try to take the biggest problem first, and go from there.
Have you had an MRI of your brain? If you can let us know specifically what the most important issue is for you at this time, we can find resources for you one chunk at a time.
Thank you for writing. I have a background in ortho and neuroscience nursing, so hopefully I can at least help point you toward some resources.