Of course, Stalin knew all about the US atomic program, from his many spies in that program. Stalin is still working hard to ingratiate himself with the Brits and Americans, although they now see that they have less need of his military assistance.
The British and Americans are planning a 1946 Big Three meeting in Washington, leading to a postwar Peace Conference. Stalin almost certainly had no intention of attending as he never left the area controlled by the Red Army.
Stalin wants the Japanese to hold out a little longer so he can replace them in Manchuria and Korea just like he replaced the Germans in Eastern Europe.
And where the Red Army goes, the Commissars follow like camp whores. Or like cockroaches; once they infest your country, you can’t get rid of them. It’s already obvious in Eastern Europe.
I agree with you. Of course Stalin knew. The Roosevelt Administration was rotten with communists.