Can Gale or Shadowheart still use their Illithid persuasion even if Tav has used up theirs? They should. I haven't tried but I bet they can't.
They can. Each companion can use their illithid power once a day, just like Tav.
Does each different usage count toward getting the powers?
If so I'm pretty sure if done right one could get enough uses(was it 3 or 4) to activate the sickness scene & powers for all before they take their first long rest. I wonder if you have to do each dream step first or not.
