Speaking of PRC, you made a right call of Cultural Revolution still occur as IOTL, it could even get worse, since Soviet became even more "Revisionist" ITTL. For me as a Hongkonger, I have a mix feeling - it could went worse it at least three ways - Deng Xiaoping died, in long run butterfly into
"birdcage economy" orient Chen Yun leadership late 1970's onward, therefore a British Hong Kong was still needed for the only major outlet for hard currency, and Handover of Sovereignty would at least be much delayed; or worse, Zhou Enlai lost control in foreign policy,
Macau's 12-3 incident and
Hong Kong 1967 leftist riots could ended in premature reunification of this to these places; or worst both scenarios happen. But in either cases,
Détente and establishment of diplomatic relation between PRC and USA would be delayed for a long time, and one last dark notes:
during OTL 1969, Soviet came close to launch a preempt nuclear strike Chinese nuclear facilities, it's seems more likely to happen ITTL...