Regarding Svoloch
Solution 1:
No, it's not the same person. "Svoloch/Сволочь" in russian means "Bastard". The one in World at War was just some sniper, which was shot and killed in mid of Vendetta mission. The one in Black ops 1, Vorkuta (Gulag), was just some Prison Guard, which Reznov called "Svoloch", Bastard.
The Sniper in Vendetta was German, and the Prison Guard in Vorkuta was Russian and those two events were ~21 years apart from each other.