It's impressive that you went through all that trouble, but I'm afraid, sometimes RNGsus simply hates you. One time, I was farming the Fire Dungeon for SIX HOURS just to get one measly pair of Molten Greaves from the Lava Golems. I had multiple instances like this, but Spedu told me every time that the drop rates were correct. About the other thing you said, where exactly does it state that you can get only one item of that type per battle? Just because there's not a specific number next to the items on the loot sheets doesn't mean that you can get only one of them at a time.