The accuracy of a ballistic missile is measured as 'Circular Error Probable' (CEP). This is the radius of the circle within which 50% of the missiles would be expected to land.
For Thor, this figure varies between 300m to 3km - for the purpose of demonstration I have used a mid-value of 2km.
Using RAF Driffield as the centre, the percentage of missiles landing within 1xCEP, 2xCEP, 3xCEP are marked in shades of green
The diagram shows that 99% of missiles would be expected to land within 3xCEP or 6km of the target
The 1.44MT warhead was powerful enough to kill everything within an 8km radius (note that Hiroshima was 0.15MT).
A 1.44MT explosion affects a much larger area than just the zone of 'death & destruction'
Severe burns and smashed windows would threaten a much wider area
Note: Although Thor is now an old weapon, the current nuclear warheads fitted to a Trident missile are typically less than 0.5MT
However, the quoted CEP for a Trident missile is less than 100m.