3rd party controllers tend to be better for pressing all directions at once. Sadly this may not work, even if it does it will still need additional outlay.
At some point you'll have to decide whether it's better to just return it to Nintendo and play dumb as to how it got broken.
I'm not altogether sure how your Wii got bricked, you mentioned Neogamma but that wouldn't black screen you if it went wrong.
The only ways you get a black screen are usually down to removal or messing with System IOS and System Menu files. All other types of brick usually give you corrupted messages.