There's gotta be something else going on here and I'm gonna guess it might be your SD card. The only thing left I can recommend is do a chkdsk(scan for bad sectors junk). However.. I've had the apploader issue before and what happened was I chose the wrong convert method. You're already using Extracted though. I'd try another loader like PostLoader or WiiFlow and see what errors those give you. If they STILL give you errors and you've already tried running a chkdsk then the only other solution is to use another ISO because chances are if all else fails its because the game itself is to blame. Of course if THAT fails you might want to try another SD card or USB drive.
Also it's not uncommon if SD formatter says your SD card doesn't support full erase because it says that about my SD card too(actually its Micro SD with SD adapter). What you want to select is Full (OverWrite).
WiiFlow gives me "app_entry not within the apploader area!".
Just did everything you suggested, still getting the same error. I'm going to try another SD card.