I just noticed something, too. You said you used Transpose and it was "supposedly restore the whole MP bar, which does not happen". That's not how transpose works. All it does is make Astral Fire go to Umbral Ice (and vice-versa), without having to cast two Fire or two Blizzard spells to do it. After transposing from Astral Fire into Umbral Ice, you cast more Blizzards and THIS is what fills your MP bar. At higher levels it seems almost instantaneous, because Umbral Ice III has a ridiculous MP regen rate.