Hi sc4rppph,
As a disclaimer, I don't use Floquet ports, but the setup looks correct to me as far as I know (HFSS 13). For the master/slave boundaries, you probably just want to use the specified phase angle rather than theta/phi for square structures. To get the dispersion diagram, set the phase angle of Slave X to a variable AngleX and phase angle of Slave Y to variable AngleY. Using Brillouin zone notation, Gamma to X is SlaveY = 0 and SlaveX varies from 0 to 180 degrees.