Skype on Mac: How to get DAW (Cubase) output as Skype input?

Not sure.

A workaround would be to send the channels you want to a free output of your interface, then connect a cable from that output to the input skype defaults to.
 
^ looks like it may work, but I cannot figure out how to make Cubase show up in it. Skype shows up but not Cubase. :(

EDIT: Ok got Cubase to show up by selecting Jack as the driver in Cubase, but the "routing" window in Jack is fucking retarded... still can't get Cubase's audio to be Skype's input.
 
the simpliest way is to use two interfaces. Skype only recognizes inputs. Cubase is a return.

You could take 1/8" cable from interface headphone out to internal audio line in.

Skype is mono so you could route output 3 of your interface to input 3 (doesn't matter which) use the sends in Cubase to go to to out 3.