Okay thats basically is saying the shader is going a bit mad there stwert, This may be why the lightmap isnt writng, Ive had this in the past. It sahould just create it with the shader when hit the create node and do the first render. But usually once the lightmap writes you shouldnt really worry. SSS is a killer anyway on render time.

As for making a pass of it, Ive heard Maya doesnt do it properly as a pass unfortunately. Its a bit crap like that.