Alexander, I'm not sure if this could help, but try -B. It allows you to set black brightness in cd/m^2.-f1 -k0 -A20 -B0.1 worked for me but my problem was color hue in darkest grays.
-B0.1 was the lowest I could set in dispcalGUI. //www.freelists.org/post/argyllcms/Problem-with-110-RC2,16 Andrzej Duda