Here's my explanation for the whole "Phoenix Down" argument. When a character goes down in battle in an FF game, they don't die. They are knocked unconscious. They black out and the only thing that can instantly revive them is a Phoenix Down. In the "tutorial" segments of the FF games, they never once say that Phoenix Downs revive a character from "death." They always say that Phoenix Downs revive a character from "unconsciousness." And there is a big difference between being knocked unconscious and being put to sleep with a sleep spell.

As for the Soft question, I always assumed that Palom and Porom couldn't be healed because they turned themselves to stone in order to save everyone. It was their choice to sacrifice themselves for the good of the team, and a simple curative item would have been incapable of altering the strong wills of two human beings.