I also have RSD in my right ankle and after 5 years and 10 different doctors I found the right one who gave me the right diagnosis. I actually found him when my orthopedist wanted to do an ankle fusion and the idea just didn't sit right with me so I decided to go to a pain management specialist for a 2nd opinion. Unfortunately, RSD can spread as it gets worse and any stress or trauma to the body can cause it to become worse. That can be stress in your life, an ear infection, sinus infection, the flu. An amputation is absolutely a stress and trauma to the body, which could cause it to spread to other limbs and be even worse than it is currently. I too have the ketamine compound ointment, which is very expensive. Unfortunately it only helps me if I use a lot along with saran wrap to help it absorb (per doctor's recommendation when just normal use did not work). The saran wrap was just too painful for me to use. I also use the patch but 75mg along wiith Opana instant release 10mg or Morphine instant Release 30mg depending on the breakthrough pain each day. I have had many sympathetic blocks as well as trigger point injections. A TENS unit (electrical stimulation) can bring some relief as well as tools learned in Physical Therapy. In less than two weeks I will be having a spinal cord stimulator trial as my overall pain is getting worse as well as color and skin quality, my doctor is fearful of it spreading to other limbs. I am guessing since the doctor you mention is speaking of amputation than he or she is not a Pain Management doctor. If you have not already seen one that would be my recommendation because they will at least have experience with RSD whereas many PCP have not and as my doctor explained orthopedists often believe surgery is the answer and rarely diagnose RSD because there is a chance their work inadvertently triggered the RSD. I saw many doctors who were supposed to be ankle specialists but because nothing showed on the MRI, their response was "I don't know what is wrong, you are stuck with the pain - Have a nice day."
I wish you success in finding the answers and relief you so desperately need, but please do not go the route of amputation as it will make things so much worse if RSD is the main diagnosis.