I didn't read the whole thread so sorry if I'm repeating someone. Have you tried physical therapy? The reason I ask is I used to get what you described w/the back going out & not being able to walk. I didn't go to PT but I learned the low stress exercises online & started doing them even though it hurts like a biåtch. Since strengthening my muscles I haven't had my back go out on me, it still hurts everyday but I can live w/pain. BTW, I have L1,L2,S1,S2 herniations & lumbar stenosis(the specialist said I had a back of a 70 year old @ 16). It's been over 10 years since I seen a doc for it so there's probably more going on now. Good luck though & hope it gets better.