Help with Civil 3D Assemblies

I have a specific roadway typical section I need to model using AutoCad Civil 3D 2009 and not real sure on the best way to do this. The problem I'm encountering is in the fill conditions and applying the 1' deep toe ditch.

1) In a cut situation I need a 3:1 cut slope for a minumum depth of 3' and 1' below top of sub-grade and then 3:1 to natural ground

2) In a fill situation I need a 3:1 fill slope to natural ground and IF a 3:1 back slope can be applied, I need a 1' deep toe ditch. So If 3:1 back slope can be applied, I need to go 1' below natural ground with my fill slope. If it can't be applied then the fill slope just simply needs to tie to natural.

3) I also am having trouble or a case of ignorance on how to apply a different sub-grade slope than that of the surface.

Thanks for you help!