I think the Soviets would probably include Chinese targets in the event of an all-out nuclear exchange; they were very much in the American camp, Cold-War-wise by then, weren't they? Although I'm sure the US kept their options open...
(I vaguely remember some not-really-funny anecdote from the time of the Cuban Missile Crisis, when Kennedy found out that the SIOP plan for a full-on exchange included all sorts of targets in China, who weren't even involved in the crisis. Basically, the DoD and SAC told him that it'd be too difficult to redraw the plan at this short notice, and besides they were all commies anyway...

)
As regards a TL based on an early-80s nuclear war, I agree it'd probably end up being...short... However, I remember in
Threads and
The Day After, they did continue the stories after the actual exchange, showed martial law etc being put into place.
Threads, in particular, showed the effects of the war for years afterwards, with most of the survivors being rounded up and put into work camps, iirc, and it was implied that this eventually became a new form of feudalism. In the last part, which I think was set twenty years after the war, the population of the UK was the same as it had been in 1400, and the survivors were just barely surviving (not for very much longer, perhaps) in a dark, cold world, nearly all of them with either cancer or severe birth defects. Was even this portrayal wildly optimistic, though, I wonder?