I suspect Russia is worried about how well their nukes will work. The small tactical ones (battlefield nukes) are the most complex and so most at risk of a maintenance failure.

Russia’s worst fear is deploying a nuke, only to have it fizzle. At this point it’s strategic or nothing. Deploying a strategic nuke would cause massive political fallout. Far more than Russia could cope with. No-one, including China and India, want that genie back out of the bottle.

It implies the trend is likely to continue. That the searched areas and the unsearched areas are nominally the same.

E.g. An inspector saying they have found 20 problems, this far, while 50% finished implies they expect to find 40ish overall.

Finding zero problems thus far implies you are not expecting to find many/any, if the trend continues.

Not quite.

Yet implies they expect to.

Thus far is more neutral, erring towards not expecting to find anything.

Vaccines do increase autism numbers.

Most childhood vaccines are administered before symptoms of autism generally appear. A lot of children owed their lives to vaccines, and so got to develop autism, rather than dying.