Not my area of expertise, but it sounds like a deep ocean impact would not be completely catastrophic.
With only ∼1% of the asteroid kinetic energy being converted into tsunami waves and with the stronger decay with distance implies that moderate size asteroids (100–500 m in diameter) striking the deep ocean basins off the continental shelves are not a significant overall hazard...
So like a 50% chance it wouldn't be that bad. Larger asteroids would vaporize enough ocean water to cause long lasting atmospheric affects.
Otherwise, a land impact would be somewhere in the 1-100 Tsar Bomba range energy wise.
Even that could be pretty bad if it turns out the object has lower Albedo than estimated. The difference between 500 meters and 1000 meters isn't all that big in terms of astronomical observations of a fast moving object and the composition is also quite uncertain and could add another factor of three or so to the potential impact. It could be very bad everywhere.
If you're looking at the "closest approach" distribution, that's not just for impacts, and the numbers are probability masses for the closest approach occurring on that day as opposed to some other day (not the probability of impact on that day).