I disagree about the estimation of the number of people killed. RE showed that there were people living everywhere, in every ecological niche, even underwater. The impact blew off the topsoil down to the scrith. (going by memory) The scar had to be a mile wide, and probably hundreds of miles long. Aside from the immediate impact damage, that much dirt blown into the air, and the air blast damage, and likely air superheated to plasma, would have effects well beyond the impact area. The ship probably impacted with a relative speed in the 10s of thousands of miles per hour. The impact would have been…spectacular.
And that scar is never going to heal.