hey 3run, try this if it fixes those small lines/offsets:
float D = tex2D(DEPTH,0.5 * depth.xy / depth.z + 0.5001);
I can confirm Ive had trouble getting correct depth values when I set NOSKY on the soft particle view. Put the sky back on.
In the sky material, try seting the flags ENABLE_RENDER and ENABLE_TREE. Then in the sky material's event do this:
if(render_view==soft_particle_depth) //if this view is the soft depth view
mtl=mtl_depth; //manually force the sky material to use the depth shader