I've not played around with fake stones too much, so can't really help there. I'm not sure if it's better to apply blending directly to the fake stones or use a surface layer to break up the distribution, but others maybe able to help out there.
As for the line in the terrain, try turning down the roughness in the displacment tab in the power fractal that's generating the beach terrain, as well as switching to a simple perlin noise, those lines are usually caused by the mixing of perlin ridges. You can always blend in more featured terrain inland if you choose to turn the camera that way.
Don't get too frustrated with the waves, it's something a lot of us have been banging our heads on, and no-one has yet come up with the solution. If you do, then there'll be a lot of us asking for a tutorial.
