You stated on one hand that speed limits "barely" reduce the car death rate. Your evidence here implies that higher speed limits actually decrease road accident rates. These statements are contradictory.
I changed my mind on this based on the evidence that I discovered. I was initially comparing German accident rates to Spanish ones, but then I realized both countries are low so that's an unfair comparison.
However at the same time, if you look closely, China has more road accident rates despite supposedly having higher speed limits.
Maybe there is a lurking variable there in that the Chinese have worse roads so there will be more accidents. The road quality in western countries is comparable.
In addition, there exist various studies that definitively show that higher speed limits result in increased accident rate and accident severity.
I don't know where these studies are, but if that is the case, we would have to see how much speed limits reduce the accident rate and if the restriction in how fast you can drive on the road is worth the lives saved. If only 1 life worldwide gets saved by making the speed limit 10 kph less, it's not worth it. Freedom is a trade off.