The sequel will follow the ending where you kill both Demichev and Barisov...And Renko will be the new Big Bad. The third ending sequence implies that Renko ends up becoming a merciless dictator like Demichev. It's very likely that Renko will grow unsatisfied with merely ruling the old USA, and launch a Take Over the World campaign, and it'll be the job of the new protagonist to stop him.
Singularity is an alternate-continuity BioShock game, with time-manipulation powers instead of Bio-Augmentation or bottled Functional MagicInfinite states "There's always a lighthouse, a city, and a man". The Demichev Reactor, the Katorga-12 facility, and Renko could be seen as fulfilling that criteria. The TMD takes the role of plasmids/vigours. That's the reason it's so similar.
There is no Translation Convention with the signs in English in KatorgaWith an incredible scientific discovery like E99, it's hard to not think that the Soviet governement would have pursued the help of scientists from outside the USSR, even leading some to defect their own countries just to research it. This, however, made necessaary to use signs of another language to help them around, and English was the most obvious choice.