Can you please link to "per-night homeless statistics from UN" source that you mentioned? I can't not find it through a little googling.
5 million figure for Russia for example appears on wikipedia [1] where it is cited from IB Times[2]. IB Times[2] cites Homeless World Cup[3] as the source. Homeless World Cup[3] cites the original IB Times[2] article as the source for the 5 million number! This was the first number I investigated and it already seems super suspect.