Hello phrenzy84!
I have similiar issues with SSS when the model not closed on the bottom. You need to use polycap node with triangulate option switched on.
So, here results of such operation:
Render before:
After applying node:
About dark and green areas - try to play with lights, attenuation density and scattering phase. On the model above I have density at 20 and phase at 0.1, environment light and two area lights.