Can't help with info about lumbar sympathetic blocks but just wanted to ask if you have been checked out for a vascular blood flow issue causing the chronic leg pain?
I ask because, whille I don't have a leg pain issue from it myself, I have renal Nutcracker Syndrome (NCS) and this can be a 'mystery cause' of leg pain. Or if not this, then iliac vein compression (May-Thurner Syndrome) can be another (standalone) mystery cause of leg pain, and not uncommon to also occur as a comorbidity in those with NCS as well.