They're safe (for now) because they're reserved for the student council. Imagine how long they'd last if they weren't reserved.
And MC is safe-safe (maybe) because Kanra already planned to take him for her own personal use forever and ever. I doubt booty demon will leave the only person (human or demon) that made her feel something in here forever either. Bangs guy was already getting speedrun by the twintails demon so maybe she wants to keep him, hard to say. Can't remember anything about the two hair style guy's relationship.
As for the work, the facility director made it seem like they have 2 tasks here but I'm think that it's possible that both tasks are the same thing. Looks like each room of demons has it's own quirk, the ones next to them enjoy torture and the ones in the room they're in just wants to get to get down business.
Maybe there is a room where pigs imbue dolls with libido for demons that want to snuggle the dolls for their girls, or perhaps since they're treating libido and life as separate resources now. They "bottled" libido into the ball for some other purpose separate from feeding the girls in this room.