Those last two screenshots look amazing man, great job.
I'm thinking that it would be a good idea to only apply the detail texture to pixels which are a certain distance from the camera - does anyone know how to find the depth of a pixel in HLSL?
Is there a way you can sample the mipmaps? because they function just like that: different textures sampled based different levels of distance.
If in your app you manually create the mipmaps (instead of letting the API do that, say, with AutoGenMipmaps), then you can manually set different levels of transparency for each mipmap level texture, leaving the last level entirely transparent.
This way the more distant the ground point is, the smoother it'll be.
EDIT: This is what Super Mario Sunshine used to control the water specular effect, with manually created mip levels.