1) Mearsheimer is relying on an OBSOLETE paradigm - that aside, Moscow has already FORFEIT credibility by allowing NATO to deploy at decapitation range/allowing Ukraine to be transformed into a hyperaggressive/hostile proxy. Escalating NOW would be pointless owing to fact deterrence is null and void and Russia has (as stated) FORFEIT credibility.
2) Notwithstanding the FATAL error of allowing NATO to deploy at decap range, the strategic situation could have been salvaged if the minute Ukraine assaulted Russian territory, Russia massively RETALIATED with all available means/forces in being - including CHEMICAL and NUCLEAR munitions.
It was absolutely imperative that Russia ALSO strike Ukraine's European accomplices (with CONVENTIONAL forces) with an eye to inflict as much COUNTERVALUE attrition as possible - and to declare an intention to strike European capitals with NUCLEAR forces if they do not immediately CEASE attacks on the Russian Federation.
3) Mearsheimer has not stated what he means by ''CONTAINMENT'' vis a vis the PRC. If he is speaking about Peking's intention to dominate the South China Sea and to poach rare Earth minerals, then ''containment'' in the sense described by George Kennan (or by more HAWKISH elements such as the 'Team B' cadre) that isn't an applicable policy paradigm.
China is not going to try and dominate these key spaces and resources by conventional MILITARY means. They are doing so (and will continue to do so) by a combination of complex interdependence/incentvization by way of SOFT POWER and diplomacy, by way of shell companies that do business nominally as PRIVATE actors yet are directly accountable to the Politburo Standing Committee and the PLA, and by way of exploiting ethnic and sectarian divisions in Central Asia, Africa, and within their immediate sphere of influence.
Mearsheimer is not capable of understanding the 20th Century as an extreme OUTLIER - and he is incapable of recognizing the relevant variables on display within the conflict cycle of 1914-1989 as historically CONTINGENT and not as constant factors that characterize power-political activity.