1.
nlprint(transmission_spectrum.current())
See the manual (http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.transmissionspectrum.html)
2. ATK 11.2 is equally excellent ;) See this mini-tutorial (http://quantumwise.com/publications/tutorials/mini-tutorials/98-i-v-curve-and-voltage-drop).