Symmetrical legs & feet; numb, weak & tingly. painful to walk @rest, both feet throb til they both go "numb". is this due to my chronic back pain?

Maybe: May be your back but also may be diabetes, blood supply to feet (though not likely).

Doubtful : Pain that is symmetric suggests other causes especially when only involving the feet. Possibilities include poor circulation, neuropathy (abnormal nerve function from diabetes, medicines, chemical exposures). Peripheral nerve entrapment (like carpal tunnel in the wrist) can also occur. Spinal problems possible, but less likely in my judgement.