@versub The curse isnt to sleep a full day, it is to sleep an incrementing amount of time each time you use magic, the final (as in, the one that was longer than is manageable) being longer than a lifetime (as they said noone has ever woken). Splitting it would mean that the time splits likely yeah, but it would still be ridiculously long, and I assume mean all of them fall asleep if any one of them uses magic?
As for cat curse, I guess they all become nekomimis at first. This one seem to progress without using magic, so I assume it means that after thrice the timespan, all three are fully cats?
The machine curse is simple. Like cat curse it is in effect even without using magic, but it seems to be a constant field of effect, and not something that progresses. Meaning it would merely be a third as strong. The radius should be a third, but I am unsure if the "doesnt work" is binary, or dependent on strength of the field.