Already shifting the goalposts I see. The eight hours figure is for how long it takes to fuel the weapons. However, the Soviets kept around a quarter of the missiles fueled during the crisis on a rotating basis. While it would take 20-minutes from even this state to fire, that’s still enough time that possibly a number of the weapons might get away.
You have a reference for the 1/4 fueled statistic? The R-16 could stay fueled for 30 days so the alternating schedule doesn't make sense. In general it was rare for the R-16 to be on pad alert (1.5 hr to launch) but I've never seen any data that specifically looks at the CMC readiness state.
To answer the OP question, depending on the circumstances behind nuclear release you could see anywhere from 0-5 cities at the best case to 50 or so in the worst case. Best case would be US first strike on Cuba at USSR - if they catch all the SS-4 and SS-5s and hit most of the ICBMs and bombers while on pad alert NORAD can probably clean up most of the stragglers.
In a Soviet first strike you have the 36 R-16s, the Bears and Bisons with 250 or so devices and the 10 or so operational SS-4 in Cuba. With reliability issues, operational losses and NORAD figure maybe 50% effectiveness which gives you about 150 detonations. Some of those will be military targets and some cities will be double or triple targeted (DC, NY, etc.) so figure 50-75 major cities gone.
Since Washington D.C. is very unlikely to survive a CMC WW3 without at least one nuclear strike IMO what city would serve as the new or temporary us capital after WW3?
Probably Denver if no issues with fallout from Ent/Colorado Springs.