Let me repeat this: Technological advancement alone can't bring down a government, as long as the necessary economic reforms are gradual, smooth, and provides much inclusive growth for the economy, since the disillusionment effect of failed reforms then followed by rapid reforms would not be existent in the two countries ITTL.
My issues are a lot with your stories. It is very forced to get your desired ending. Nor did you understand what I meant. Since political freedom is very different from economic freedom.
The most believable part of Soviet wank is increasing production since it was the Soviet managers who were afraid of the Ratchett effect. Now, for quality control and technological advancement is very far from how Germany, Japan, USA does it or their system since quality control and technological advancement would drive price very high nor does the Soviet in OTL or your ATL have a better system in terms of quality control or technological advancement than the USA.
The USSR, although authoritarian, did have its own bunch of geniuses that were not utilized by the hardliners. The reformists did want reform, and were adamant that the people participate, under the condition that they won't call for the ousting of the Party. The people were fine with this, but because these reforms weren't enacted IOTL earlier, they became radicalized.
Authoritarianism, if led by the proper leaders, could have become technologically advanced.
If you can predict what technology or those who is going to discover them yes. But you cannot.
You have to let the people be part in control of the economy to drive technology in all aspects. But for central planning or any state oversight, technology is limited to what the politicians deemed as future technology not by the inventors themselves.
Authoritarianism can be in certain aspects. But it is the same problem as the Soviet-Type planned economy. The ones involve in planning/government controls are not inventors nor the most creative people but politcians, in the case of Soviets and Red China, limited to the Communist party. In the US type economy, technological advancement is two fold, one funded by the state close to the one you described e.g. DARPA/Manhattan project(politcian drive), the other funded and controlled by the private sector, like Apple,Facebook, Ford etc. which the state has no control(inventor /individual driven).
You can say that Authoritarianism will be more advance in certain aspects wherein the state focused more money than a US Mixed economy. But will never be more advance in all other aspects nor any quality control. Example in OTL would be North Korea vs South Korea. North korea is more advance in ICBMs/Nuclear weapons. But South korea is more advance in everything else.