I'm just wondering if you have seen an orthopedic surgeon for an evaluation, or someone other than the chiropractor concerning the heel lifts, etc? I usually post on the back problems board, but just happened to notice your post. I have had three back surgeries (lumbar) and work with a guy I call my "rearranger," for lack of a better description of what he does.
I am wondering if you truly need the lift or if you are having problems with structural alignment that is pulling your pelvis into rotation, which causes you to carry one hip higher than the other....this is a not unusual problem among people who have back issues. It can also cause the scoliosis, if this is something that you have developed somewhat recently.
Usually having a tilted pelvis is a result of improper alignment that causes some ligaments to shorten and others to lengthen. It is not a condition that you can't do something about....(usually...
I just throw out this possibility as another option for you to think about -- your back problems may be causing the titled or rotated pelvis...and consequently, the foot problems. When I first went in for my sciatic pain, the first thing my surgeon did was look at my feet and evaluate the way I stand...it is all so inter-connected.