An uncertainty about the Lebanese civil war.

  Agree and also the idea that people like Khruschev and Gorbachev - who could well be a non-entity in TTL - being sent to the gulags extending the USSR's life for decades.  Khruschev probably extended its life by giving it more responsible government [albeit not by much].  The USSR didn't collapse because Gorbachev came to power.  The reason he was selected as leader was because even the old guard apparatchiks realised that drastic change was necessary and the big impact of Gorbachev's character was that it died relatively bloodlessly rather than with a lot - potentially far, far more deaths.

  Even if this happens then some of the other issues are unlikely.  The Soviets seeking to help Mossadegh would only increase US and UK hostility towards him it being already deep in the cold war.  You could end up triggering a major conflict.

  Similarly assuming that the something like the Iran/Iraq war still occurs would be a huge step.  If it did then why would a USSR under conservative rule be any more interested in and successful at defusing the conflict that OTL.  Assuming no significant butterflies Iran is under a religious fanatic who hates the Soviets nearly as much as the US and Iraq is a Soviet ally.  Moscow is unlikely to be willing or - unless it makes dire threats to an ally to prevent it attacking a mutual foe - able to prevent Saddam attacking Iran.  Saddam attacked because he saw Iran as gravely divided - which to a degree it was - and that he could win a quick war which would both boost his prestige and capture the primary oil producing region of Iran and add it to Iraq's own resources.