1) On the ship on the biggining you can eavesdrop and hear Crescent talking with your mother and saying that she wants to see your smile and after the mt. Valor events it becomes clear that she cares for you, while Gardevoir doesn't seem to. I'm sure that Gardevoir will reapear later on. I'm also intrested to see the players' relationship with Crescent.
2) That may be the case.
3) If it is the case then the specific Absol could be the one that you met with Melia on the Goldenwood forest. But I don't think so because Gardevoir is evil while the prophesy of light is good and Absol is known as the destruction pokemon and Gardevoir is generaly loyal and good it may be just a symbolysm.