God damnit man, watch the discussion. It's at 1hr 20 min. Even the glober arguing for it is more clued up on this than you are.
Discussion
I didn't make it to the discussion about electrostatics on the video, it's just too long. If you can point to a specific minute, I can analyze it.
I won't argue that electrostatics and gravity are related. They are, and that's why a field called "electrogravitics" exists. But that has nothing to do with the Cavendish experiment.