I still can't tell which direction this score goes... Does a decreasing score mean it is "less safe" (i.e. "more violent") or does it mean it is "less violent" (i.e. "more safe")?

I can't speak to Germany, but we also have "end of speed limit" signs in California, and here they definitely mean what the other commenters have said, i.e. the basic speed rule applies. Just based on reading these comments, the German rules seem to be the same here, so I would very much suspect that that in your example the speed limit is unambiguously 100km/hr after the "end of limit" sign.

I say this as an American... I can't help but feel that the US will be judged to have been on the wrong side of history in virtually every topic for which there are sides in the last decade if not longer. For reasons I don't understand, we seem to be actively and aggressively working to destroy our country and as many global institutions as we can.

As far as I can tell, Asahi actually requires dual boot. There doesn't seem to be an option to install it standalone. (But I have an M4 Air, so I'm not able to install it yet)

Would you not? It would look odd and draw a lot of attention simply for being unusual, but I'm struggling to come up with any way in which doing so would actually harm me.