I don't think you are going to be able to separate the roots. I would just un-pot it and cut the old stump off as cleanly as you can. An old bread knife works well if you don't have a machete. There used to be a banana research station near where we lived and they would just hack off the pups and any attached roots would be cut off before it was replanted. I would not strip off any roots from your pup this time of year, just get rid of the old stump. and add fresh potting medium. Use the largest pot you can find that fits your spot. (maybe tell the spouse to get a smaller vehicle.
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