Cool, looking pretty much spot on!
Terrain surface rendering in RWR is based on the well known texture splatting technique (e.g.
https://en.wikipedia.org/wiki/Texture_splatting), with alpha blending done using alpha rejection to achieve sharp edges between layers. Additionally, various higher detail noise maps are used to manipulate the value originating from the map-wide splat map for each layer to cause higher resolution distortion between layers.
Furthermore, the layer edges are accentuated with some colorization, usually something dark to make them have those cartoony outlines. The vertex and pixel shaders themselves, and plenty of old, non-used or otherwise experimental shader code, can be found if you unzip media/data1.pak and look into terrain.*.
The dynamic surface effects, blood splats, tire marks, snow and such are done with pretty much the same technique, just rendered as a second pass over the actual terrain.
I hope that answered the question at least in part!