You seem to have considered all the performance issues, it’s strange that you cannot get 60FPS. It works totally fine for me.
Here are some more things you could check/double check.
-Energy saving mode on the device off
-Only materials with “fully rough” enabled, no normal maps. Also on skeletal meshes.
-No translucent materials
-No stationary/moveable directional light
Try setting the Android Device profile to this:
Also you could try the game in an empty level, with just a basic ground that uses a simple color without any textures or the skybox. And just a static skylight.
As for fog, you would need to fake it. Either by using a spherical mesh around the level with a scenedepth fog material and depth test disabled. Or using pixeldepth(see cameradepthfade function) for all your level materials to create a simple distance fog. The second method is ALOT cheaper, especially if you use it in the vertex shader.