  We demonstrate that the differential conductance, $dI/dV$, measured via
spectroscopic imaging scanning tunneling microscopy in the doped iron
chalcogenide FeSe$_{0.45}$Te$_{0.55}$, possesses a series of characteristic
features that allow one to extract the orbital structure of the superconducting
gaps. This yields nearly isotropic superconducting gaps on the two hole-like
Fermi surfaces, and a strongly anisotropic gap on the electron-like Fermi
surface. Moreover, we show that the pinning of nematic fluctuations by defects
can give rise to a dumbbell-like spatial structure of the induced impurity
bound states, and explains the related $C_2$-symmetry in the Fourier
transformed differential conductance.
