Wow man, that atmo is really sweet

I see you cranked the light settings pretty much...too much to my taste, because the grass and trees lack shadows now.
Maybe you could lower your light settings back to your original 'dark' version and then add a light opposite to the sun angle and direction.
This lightsource casts no shadows or anything and strength = 0.2 - 0.4. This way you can easily control lightness of shadows without losing the natural sense of lighting.
Another nice thing to try maybe is to add some (more, if you already did) specularity to the grasses (like the patchy distribution). Some translucency will also greatly add to realism.
If you feel up to putting more and more work into this

Martin