Welcome to NeuroTalk:

Are you sure you took B-complex 1000mg? Do you still have the bottle, and could you type in the contents with dosage?

The NeuroMet may work better for you if you take it on an empty stomach. Have you had blood tests to show your B12 level to see if it is working or not?

Gabapentin may cause swelling in the legs and feet of some patients. That is pretty common.

The symptoms you mention can be from many things.
The most common is impaired glucose tolerance. If you have periods of low blood sugar you can get tingling etc.
You can get this from low thyroid functioning.
You can get this from exposure to toxins or heavy metals in
the environment. And you can get this from gluten intolerance.
So there are many things you can look at.

Also low Vit D may cause tingling by reducing absorption of calcium from the diet.