Damage dealt is always this formula: Level * Weapon Power + rand (0, 255)
I don't know how BSiron got some random number to be added.
Damage ignores target's armor, so Defense = 0 in the calculations.
Ignore all other properties of the weapon, whether beneficial or not.
Row is irrelevent for this attack (Edge's or the enemy).
Note: If you don't use the duplication trick, the best weapon to throw are dropped Dragoon Spears. In FF4A, you could just buy the expensive Assassin Daggers and throw those. In FF4ET, the retweaked power of the Fuma Shurikens (100) are enough for almost 9999 damage.