Been to Rochechouart. Seen the crater, been to the museum.
Problem is that that saurful of ambience is genuinely too small to have caused a mass extinction unless the climate was stressed out to the point of causing a mass extinction at the exact time.
At that point the mass extinction would be a result of the darkness switching off photosynthesis for between 3 & 6 months (resulting in a pelagic oceanic mass extinction based on phytoplankton. followed by a CO2 spike suffocating maladapted land lifeforms requiring high O2 levels.
A 2nd crater at the same time with a larger footprint may be required to result in an impact extinction hypothesis.
I am currently likely in the case of the end Permian to regard the mass extinction culprit to be the Siberian traps which is a continental example of a large plateau basalt province resulting from an upwelling mantle plume. For size comparison, the only similar example would be the marine (now 3 way split) early cretaceous example of the Ontong Java plateau, with the Siberian traps (largely eroded) being previously bigger than Ontong Java.
Also note that at the time, the shape of Pangaea would result in a climate mode exactly the same as the Jason model (mode#2) which is extremely inefficient at cooling the planet. ie. a fixed dry monsoonal flow from equator to pole covering each lobe of Pangaea dependent on season, with the bulk of the rainfall in the centre of the Tethys ocean (tropics & temperate rainbelt) at the antipodes of Pangaea on the opposite side of the planet.
Result would have been a climate "heat bath" that the current global warming officionados are touting for the future here if the climate mode~2 were the only mode available (currently the Pleistocene shows 4 modes, 2 of which are much more efficient).
For the record, Ontong Java erupted during climate mode#3 and the Earth (albeit warm) did not overheat!
Have a nice day: Ag