The Hashimoto's causes peripheral neuropathy. It is reversible depending on how long you've had the disorder. For myself it might not be completely reversible.

I have symptoms of: muscle loss in arms and back, tingling sensations in the arms/tricep/forearms/upperback, and a burning sensation - due to the nerve irriation damage. And muscle weakness.

T4 and T3 should be used for replacement therapy together. In preparations such as Thyrolar. T4 only replacement will cause lingering symptoms of hypothyroidism to continue. Due to impaired T4/T3 conversion and Reverse T3 increasing in many people further slowing metabolism. This is why if you are on say 100mcg of T4 you should add 25mcg of T3 to it.

Peoples dosages depend on where their symptoms resolve some people do well on 100mcg T4, 25mcg T3. Some are on 200mcg T4 and 50mcg of T3. It depends on the person. Their are even people who only respond to T3 - Cytomel only which completely resolves their symptoms.

If you've had enough of thyroid problems check out this website for helpful information on how to be your own doctor:

http://www.stopthethyroidmadness.com/

In regards to peripheral neuropathy what i have found to work is ultra-high doses of MethylB12 anywhere from 20-30grams per day.

Another nutrient called Benfotiamine which is the fat soluble form of Vitamin B1 has also been extremely helpful for relieving PN symptoms in many people.

http://www.mcvitamins.com/neuropathy.htm

Your best bet is to find the underlying cause of your neuropathy and treat it vigorously as soon as possible so it doesn't get worse.