Hi, one question, do you mean K-5s were used by the military during the Winter War, or in use as airliners at the time of the Winter War? The Kalinin K-5 was built in what were considered sizeable numbers for a Soviet type (built in Ukraine), with around 260 built by 1934. Reportedly it was an efficient type, economically as well. I can't see any reference to use by the military in 1940, by then, it was an outdated design, and the air force and airlines were equipped by more modern types.
Iosif Nieman or Nyeman was the designer for the Kharkovskii Aviatsonii Institut. What little I have on these aircraft is that the KhAI-1VV (for VVS), or the KhAI-1B was produced for bomber training, with a 200 kg load of practise bombs hung vertically in the fuselage. It had two machine guns mounted in flexible mounts. Only two were built.