Hi Liz & Welcome to the forum,
I would be getting on to a neuro that is a PN specialist, that will give you all the tests needed to hopefully find what is causing this.
Next i would get a copy of all tests that have already been done, if you go to http://www.lizajane.org/ download using Excel, fill in your tests that have been done already, that way you can even post them onto the forum or just keep them for comparison reasons as time goes on, you will also find all the other tests that can be done for PN there as well.
People with Alcoholic Neuropathy normally have very little B1 [thiamine] in their systems, seeing that all your vitamin tests were classed as in the normal range, yet he suggests B1, seems strange, i would be interested to know what that neuro classes as normal range with your B12 results.
I think you will find a lot of great information in the " important links and stickies " on the main page up top, good info on supplements, diet, and heaps of other important stuff that may help you.
Another great site is http://roseannster.googlepages.com/home, all about B12 well worth reading.
Anything your not sure on don't hesitate to ask, there really are some very knowledgeable people here that will help if they can.

good luck
Brian