Nice to see the scene animated and explore some other parts of it. It doesn't look half bad.
The flickering is almost certainly due to GI. You can adjust settings to help (usually increasing GI Sample Quality and GI Blur, and enabling Supersample Prepass, all of which will increase render time), or you can simply use a fill light setup instead of GI. There is an example of such a setup posted as a sticky in the File Sharing area of the forum.
The shadow issue you mentioned would probably be fixed by using the "Ray Detail Region" settings in the Advanced tab of the Renderer node. Change it to Detail in Camera and use a value of 0.5 or 1.0. These settings are specifically designed to handle those kinds of issues. Basically what it does is extend the area of detected terrain detail further outside of the view of the camera, so that for example if a mountain is off camera and casting a shadow onto terrain that is on camera, it will have enough detail to render correctly and not "pop" as the camera moves.
- Oshyan