Russia has so far demonstrated that it isn’t capable of much on that front. Ukraine is a big country, they’re barely doing a city at a time, and they’ve only had success on a small front that they’re very familiar with.

-The sanctions were ultimately ineffective, for the reasons you explain above

This remains to be seen - they’re definitely “effective” because they’re changing everything, question is how the West could be “miscalculating”.

-China takes Taiwan during major US political unrest, at BEST destroying the fabs and at worst gaining full control of the leading 3nm/2nm etc process

That would require China to launch an enormous large scale operation, which they’ve just seen can be a total shit show. An invasion would probably not allow them to “take” the 2-3nm process either, and it wouldn’t give them the returns on the investment. Most importantly China currently does not need to be invading Taiwan to be in an advantageous strategic position - they’re “winning” as is.

-A deeper China-Russia alliance, which was expedited by our ineffective sanctions now, puts the screws to US/western companies by blocking access to the latest semiconductor tech

Currently Russia has only managed to weaken and isolate itself. The symmetrical relationship Putin would need probably isn’t on the table, and Russia isn’t a worthwhile partner for China in such a terrible and toxic condition.

(Question is if putting “screws” on western companies is “bad” thing, but that’s another matter.)

All of these things worried me before the war, but Russia’s total incompetence has, if anything, greatly held back the China-Russia relationship.