I would find another doctor to evaluate the lead.
Perhaps one that is holistic (who can do chelation), and further
testing.

http://www.find-health-articles.com/...gun-injury.htm

This article explains lead's actions in the body:
http://emedicine.medscape.com/article/410113-overview

Because lead goes into bone, it may not show up as high levels in the serum at this late date. But because bone turns over every 2 yrs or so, it would be released constantly then reabsorbed.
The only thing going against the lead hypothesis would be your lack of other symptoms. But because lead is such a huge poison, I'd have a specialist evaluate you. There are environmental physicians, and that may be a good place to start, or a holistic MD.
http://www.aaemonline.org/

Medicine is an imperfect science, and labs make mistakes, and your retention of lead logically seems important at least to me.

There is a sticky thread at the top of the page here, "Neuropathy does improve"... here is the link:
http://neurotalk.psychcentral.com/thread43699.html

I would get another opinion, if it were I.