If the severe sensations he has are like a burning pain, it is likely due to diabetic neuropathy - are his blood sugars under control? What about his
HBA1C levels? If it is diabetic neuropathy - he might need nerve conduction tests and a Neurologist to advice regarding medications. If the pain is like a squeezing pain in both legs especially on walking, and makes him stop for a while, it could be spinal problems which might need an MRI scan - if you wish to consult me in person, I would be happy to examine him and advice.
Next Steps
depending on the type of leg sensation, consider an in person consultation.