Well, this is at least a start. Check if you write the linear depth to the g-buffer.
Ok, back to the inverse view matrix. I don't know XNA/SlimDX, but have you ensured, that you upload the matrix in the right order (column-major) ? Check this out by switching
float4 point_ws = mul(point_vs, InverseView);
float4 point_ws = mul(InverseView,point_vs);or use the transpose of inverseView
when doing the first color encoding test