Wow, a lot of info. First I'm optimistic because the tips are green. Planting them in "bad" sandy soil was not a good idea. When rooting cuttings the soil is critical to establishing new roots and goes a long way in weather they make it or not. Never heard of putting charcoal in there but might be a regional thing. I don't think old root hormone will hurt. Your watering habit seems normal. My opinion is the soil you planted them in is the issue. After 5 weeks you should be seeing signs of growth if cuttings were healthy. Not sure where to go from here. Personally I would replant them as is with a mixture of cactus soil and planting mix and hope for best.
I think they can be saved. Try to keep them in outside sun as much as you can.
Good luck. They look like good plants. This is advise from the west coast. Not sure what growers do in your neck of the woods😎
