Check the volume knob hahaa (:
I would recheck the input jack, maybe even take it out of the body and plug it in to make sure it isnt changing from being pressed into the body. Not sure if you have enough wire to do that.
Have you tested the amp and cable with a different guitar?
It seems as if you've hit all the typical issues. Next step would be to bring it to someone. I don't think there's a lot we could do for you here.