Gotcha. I was thinking when S3D can do that sort of thing I'd delete the lights from them

Thought I'd make your life easier by having you just turn it off.
I suppose if we knew the lumens of a typical lighthouse light we could calculate the amount is there at a given distance in RL. It's an inverse square issue with a solid angle.
To be fair, though, you were asking what settings should be in terms of visibility at range. My honest answer would be zero assuming the lighthouses are separate from the other lights you mention. None would have been lit, except the Night of December 6th.
tater