It might sound cold, but, as a whole, it seems like this war was worth it for the Union. It asserted itself as the foremost military power in the world and showed the ability of its nukes, as well as pretty much nullifying the chances of China taking Siberia from it further down the line. The money from the reparations is compounded by the assertion of military might to really make it fearsome in the eyes other communism countries. I predict Alabania rejoining the eastern bloc a couple of years after China was nuked to oblivion, and maybe the revolutions of the late eighties won't happen at all. Hell, maybe even the presidents of the individual SSRs, especially Belarus and Ukraine, won't have the guts to go up against Moscow.
Well, let's see:
- North Korea gone and the penisula has been reunified by an american ally.
- North Vietnam had make peace with the USA in term favorable to Washington or at least with an high degree of saving face.
- Fought an intercine communist war with China losing at least 3 city and a couple of millions of men, not counting wounded losing an enormous amount of soft power in Western Europe alone as a lot of national communist party will be even quicker than OTL to take their distance from Moscow, basically an earlier eurocommunism.
- China is dirty poor and even more after the war, the possibility that she can repay the URSS is the same of Germany payback the WWI reparation on schedule and so the Soviet Union had fought a costly conventional war that had spent blood and tresure and diverged a lot of needed resources...sorry, modern war don't make anyone rich unless you are the supplier that live an ocean away from the fight
- In Asia nation like Japan, South Vietnam and Korea will be even more attached to the USA due to the need of their nuclear protection umbrella...or in any case an indepedent nuclear program will be now an objective of a lot of nation basically the just signed NPT is due to quickly collapse.
- Egypt can forget all the nice toys obtained OTL, the URSS need first to rebuild his stock so is more probable that the Yom Kippur War is delayed with all the butterfly involved
So, i have a lot of difficult to see all this scenario as a win for the Soviet Union, sure she had took care of a potential adversary at geopolitical level that's also competition in the communist rank, still the entire affair has been ungodly costly...and nobody with some functioning brain cell will even think to use a nuclear warhead to resolve a revolt in East Europe as it's too risky due to NATO