A mix of half organic, half rock ought to work. So regular potting soil with an equal volume of perlite/pumice/gritty equivalent mixed in ought to work fine. Do not water right after potting your plant up, wait a week minimum. Keep your plant on the dry side for the foreseeable future. Do not water deeply on a regular basis until you see new growth on top (which realistically might be next year). Strong light is important but lots of direct overhead sun would not be helpful. Bright shade or filtered light is probably ideal when a plant is in this extreme a degree of crisis. I do not think the odds are great but I also believe one should never give up prematurely. Skip the rooting hormone, avoid fertilizer. Just cut away the soft parts until you see clean, healthy tissue, and allow cuts with a big cross section plenty of time to heal before you expose them to soil.
