I would continue the follow up with the neurologist to rule out any serious neurological issues. B12 deficiency may be an issue but there are probably other factors involved to create such pronounced symptoms. If he is a vegetarian he is at greater risk for B12 issues.
With this said, it is clear that his nerves are under some distress. This may be a result of the compression from the budging disks in his low back or something else not yet identified. A slight lenition does not quite account for the severity of his symptoms. There is no harm in supporting the nerves with nutritional approaches such as B12. Vitamin B6 is also very important for nerve function so that is one you should also consider.
Tarsal tunnel syndrome is a condition in the foot equivalent to the carpal tunnel syndrome in the wrist. This can cause symptoms of burning and shooting pain as well as numbness in certain individuals. B6 and B12 can be very helpful in supporting this type of issue. I would also have him consider a high quality fish oil to get the benefits of anti-inflammatory omega-3 fatty acids. Compression on the nerve from any cause is likely to be a result of some type of inflammation. The omega-3 fatty acids in fish oil help to reduce inflammation throughout the body.