The trick is not about giving or not help to the russians, but the way the help is given. Use the entry of the US to the war to alter the proportion of vehicles and factory gear for more ammunition and foodstuff, just enough that the soviets will have the tools to finish the job but after the war they will need more time and retooling effort for their economy and military strategic reserves to recover. That will make them think twice about the expenditure of joining the Pacific War against Japan and post-war will limit the amount of surplus they can give the communists in China and Korea.
It seems to me that if people are weaselly and duplicitous, they will cause bad things to happen to themselves and deservedly so. However monstrous Stalin and many will claim (not me but many) the whole basic idea of a Communist regime may be, it gains us nothing to say "well, turnabout, let's be amoral with them!" A person, a people, a nation that will not hold itself to ethical standards sows dragon's teeth against itself.
We should not be deliberately vicious.
Now how clever is it to organize LL so as to manipulate the Soviet economy in this way? Actually I rather suspect you are recommending doing exactly what was actually done! Certainly a lot of LL was basic economic survival goods, and as the system shook down to better meet Soviet preferences, we largely moved away from giving them weapons systems and when not giving them canned food, wheat and raw materials like rubber, gave them stuff like trucks.
So the whole case for treating them in a manipulative manner is based on their ruthlessness and disregard of human life, let alone comfort and long term health, right? Here we have a people whose citizens were already accustomed to privation and terror before Hitler attacked them. Then they managed to survive, a lot of them, unspeakable privation and horrors during the war, like the citizens of Leningrad eating the paste from wallpaper like so many silverfish, God help them. Just how clever is it to foster maldevelopment of a form where they are top-heavy with arms works up the wazoo--which again, was actually their OTL preference anyway--but hope that playing carrot and stick with food subsidies will tame them?
The Soviets did not aid the Chinese Communists by giving them borscht soup and sausages and pirogies. The Chinese had to scrounge for food like everyone else in Eurasia. Nope, it was guns, airplanes, tanks, bullets that Ivan's generosity supplied. Exactly what they would be best set up with surpluses of in this system of yours--which to be fair is I think exactly what they asked for OTL! The one thing they are set up to do well is fight a modern war, or supply a modern insurgency with modern-enough stuff for their needs.
China cannot in my view be saved from Mao (or some Chinese Communist leader--Stalin personally did not like Mao and tried to have him bumped off, unsuccessfully obviously, which shows the limits to Stalin's alleged puppet-master control) unless America is prepared to base troops there on a massive scale. That's a necessary condition, it is not sufficient! Then we'd have to build up the legitimacy of the Kuomintang or worse, try to patch in some third regime on the fly. Fundamentally it is a question of, did the KMT retain any legitimacy in Chinese eyes by this late date? My impression is, no they did not. China is going to go Red, sooner or later, unless we manage a political Hail Mary pass of unprecedented and groundless success. The only optimistic outcome is if we could somehow manufacture solid legitimacy for an anti-Communist regime, and that turned out to be way beyond our capabilities in say Vietnam; we thought we did it in the Philippines but probably we just got lucky with Ramon Magasaysay. And the Philippines are a whole different deal than China or Indochina!
But of course American leadership, perhaps for basically racist reasons but with shrewd insight, had a deathly aversion against putting large numbers of non-volunteer US troops at risk of a big ground war in east Asia; they'd never fulfill the necessary if not sufficient condition of putting a zillion GI Joes on the ground to reinforce the Nationalist defense to the degree that would be needed.