I know exactly ho you feel... I have neuropathy in my legs and feet.I can't beleive that you are on 6 - 600 mg of Gabapentin. All of my doctor's told me the absolute max is 2800 mgs of Gabapentin. They also tried me on Topamax, but I had to be weaned off of the Gababpentin first. The Topamax did not work for me.
As for the Amitriptyline I take 50 mgs at bedtime, but that doesn't work. I did have a doctor that kept increasing my Amitriptyline and got me on 150 mg, I felt my heart racing and went and saw my primary care doctor and they tested my levels found out that the oher doctor that increased my levels almost killed me.
My doctor's also have me on Cymbalta - 3-10mg tablets a day. This medication is kind of expensive.
I look for any new to try for the pain, it is just so unbearble most days.
Keep your head up! Hopefully they will something soon to help us!