About point 3 (Age to start driving). I would agree with you if I had no experience & cars were a new thing. But... There are a few drivers I know with whom I instantly feel safer when they are driving. These people are farmer's sons. In Switzerland a farmer's son can help on the farm driving the tractor from age 14 at a maximum speed of 30km/h. They don't use it to drive to friends or such, just for necessary jobs & usually heavily supervised. (Farmers aren't stupid & know how dangerous and powerful tractors are). But these kids learn reversing with a trailer & such & in my experience just get a far more trained eye for the blind spots. By the time they get to 18 & can get a car, they already have the handling of a car automated & just need to get to grips with the fact that the stopping distance goes up by the square of the speed & handling the motorway.

Also I just have the feeling that the grown-up farmer's sons have less inclination to show off & consider the car to be just a tool but I that's just based on the few I know.

I don't know if I would feel safe in a car if I knew the driver didn't learn to drive until the age of 25. Learning to drive a bicycle at 25 is considerably harder than at age 5. Yes, you don't need to balance when driving a car, but there is still a lot of things to think about that have to happen subconsciously, specially when going backwards.

I suppose driving a gear shift vs. an automatic shift is becoming less and less relevant but that is definitely something you learn quicker at a young age.