Nobody's going to be aiming at nuclear silos in the middle of nowhere that are not only designed to withstand a nuclear attack, but may well have also launched by the time your missile arrives. US early Cold War targets have been declassified. [1] We did make efforts to target airfields where nukes would have launched from (prior to the ICBM), but those were valuable and weakly defended targets, regardless of whether the enemy's ships were already airborne or not. But a large chunk of our missiles were directed towards agriculture, industry, medicine product, and a large number of targets were justified as simply "population." The Soviet targets likely would have been more or less identical.

In nuclear war the goal will not be to eliminate the enemy's military - military's can be rebuilt. At the point of nuclear war absolutely all norms and rules of conflict will have been discarded. The goal is going to be to eliminate the enemy's entire country, such that he might never be a threat again. In such a situation I'd feel far safer standing near a nuclear bunker out in the middle of nowhere than I would in the middle of a high population, high economic value urban area.

[1] - https://www.nytimes.com/2015/12/23/us/politics/1950s-us-nucl...

There's MIRV, so depends what you mean by "these things".

But also some among these 3750 are in subs, and bombers.

And as for "100 would do": Well, if they all hit their targets, maybe. But part of the reason for overkill is so that even a sneak attack that's 90% successful should trigger MAD. Well, I say "should", but more like that's the cold logical deterrence rationale.