East Germany is probably run by the Soviets the same as OTL. The only difference TTL is that Germans would be fleeing eastwards from the West instead of vice versa.
It doesn't make sense for the Soviets to ethnically cleanse East Germany. All the Germans expelled from the Sudetenland and east...
Check out Twilight of the Red Tsar by Napoleon IV. POD is Stalin surviving his stroke and living for another few years.
Edit: I realise that I misunderstood your comment. Stalin surviving his stroke would still be the main POD since it would mean prolonging the Doctor's Plot/Second Holocaust.