Do a google search for the “NeatVideo” plugin (from the makers of the NeatImage plugin for PS). It does an amazing job of cleaning up grainy video. They have a free trial version available.
At frame 1 (assuming the mask animation starts at frame 1), position the circle over the end of the mask shape. Parent the circle to the masked solid, and it should move with the mask.
“I thought I should also mention that your use of the very specifically camera related terms ‘pan’ and ‘zoom’ confused me at first, and probably confused a few other people who thought the question was going to be about Cameras in AE.”
Not sure if I understand correctly what you are trying to do. If it’s what I think, I’d try parenting both the tree and the waterfall layers to the landscape layer. Positioning and scaling the landscape layer should then take care of the other layers as well.