I’m not sure why the dynamic distance for the stationary light wouldn’t render initially unless you have a camera that is further than the distance you entered. If you use the slider and max it out that should be a distance of 200 meters (20000 cm).
Looking back at our Release notes for 4.9 I had forgotten about Modulated Shadows can be enabled for the directional light as well so that there can be a dynamic shadow cast even if the scene is statically lit. You should only need to enable this in the directional light’s details panel options. You can set the shadow color there as well if you need something a different color.
As far as performance concerns and the distance of the shadow. Shadows for dynamic lights are more expensive with the more objects and geometry vertices that is within its shadow casting range. So using a lower distance will not affect as many objects which will lower the performance cost.
Give the Modulate shadows option a try. I think that should have better performance for mobile than dynamic shadowing.