It could be x Gasteraloe "Flow"

Top maybe an Echinopsis species. Middle is a Ferocactus, maybe Ferocactus echidne Bottom maybe a Notocactus

Yup, agreed on the ID. You could probably take cuttings a few nodes long & pot them back into mother plant's pot, to make it look even more full & lush.

9 ft is not a tall ceiling, its pretty standard. All those crystals will A cut the actual light down and B cause shadows, so if you have a dark hallway I would pick functional lights over pretty lights.