> do you know how many of them are unaccounted for?

Nuclear weapons have incredibly tight tolerances to be or remain viable, those tolerances degrade over time, so they require frequent maintenance in order to stay usable. Many have been "lost" over the last 70 years, sure, but few if any of them would actually still function without state-level expertise in maintaining them - the kind of capability which could just make new ones anyway.

Sure, they could still be used as fodder for "dirty bombs" but so could a lot of things and it's much less of a concern.

They wouldn't make decent dirty bombs. The stuff in the bomb is only going to hurt you if you inhale it--and it's heavy enough that it's going to be very hard to inhale.

Dirty bombs basically just make a mess, they are not a realistic threat.

How confident are you about that? I don’t know much about fusion, plutonium implosion was hard back then but I don’t know if becomes easier with modern electronics or not, and I though gun-type uranium is straightforward once you have the enriched uranium?