To be clear, I don't believe you are a subjective idealist. I believe that your nostalgia for a once great and now lost USSR has colored your analysis, but I believe you in general are more of a materialist. My critique of certain points of yours as metaphysical or idealist is constrained to those positions.
As for the progress in China, it's already happening at a breakneck pace. Conditions are improving in China faster than anywhere else in the world. So what if they made a deal with the western devil? The soviets did so too during the NEP, the CPC revisited that idea and modified it to their contemporary conditions. Any comparison between the snake Khrushchev and Deng Xiaoping has to be understood in that Khrushchev downplayed the entirety of socialist construction thus far, creating historical pessimism, while Deng made it clear that Mao and Stalin were to be upheld, and that class struggle was alive and must be carefully fought.
The Soviet models of socialism were not idealist, nor subjective. It was materialist, worked well, and was well-suited to the Soviet Union's conditions. My issue was the idea that if, say, Bolivia's ongoing protests erupt into revolution, that they should copy some period of the Soviet Union's models of socialism, rather than learn from it and adapt to their own conditions. Bolivia's conditions are not the same as the USSR's.
As for Trotsky being for the NEP and Stalin being against it, the NEP ending early ended up being fortuitous in preparing for World War II. Had World War II not been on the horizon, then perhaps extending it may have been correct, to help develop light industry more. In China's case, their socialist market economy was handled in such a way as to rely on largely de-industrialized economies, thus the risk of war was lower while in the USSR a war was always around the corner.
As for "western Marxism," in the west it is used as a pejorative against Marxists that vulgarize Marx and Lenin, opposing socialist states. I am happy that you meant no offense by it, comrade.