The gravitational force of any planet able to be a planet appearing to be that size from Earth would devastate our planet. A wispy cloud of gas does not maintain a spherical shape. The sphere is a product of that gravity.

The rise of volcanism and earthquakes is predicted by research based on other factors, and has nothing to do with Planet X. I suspect there is a planet X, but that we don't see it because it's very far away. It's also predicted from orbital artifacts, and would not be the first planet sought because of that.

You can test yourself if a camera with a smudge on the screen would reveal a similar artifact in a dark room with a laser pointer. The lens is at a different distance from the light source than the shutter, therefore parallax makes the smudge appear to move.