Since it has not been mentioned, the
Walker spy ring data certainly would have helped the Soviets. If you want to increase the chances of a T2k Soviet SSBN surviving compared to how they would have fared in the real world, you need only have the spy ring survive longer, or simply give the Soviets more years to implement the engineering changes that the data indicated were necessary.
Personally I still keep the majority of the Soviet SSBNs in the White Sea behind a minefield (ala Red Storm Rising)