After endless tweaks and rerenderings it's done (I think...).
As I wrote, the twister's rotation is inverted, and I think this was really important. The bushes are animated and there's another car and another guy. Also an idiot, because he didn't stay in the car.
I had to cheat a little: I added the splashes on the car, which are basically the same objects like the splashes on the road, but unfortunately after adding those, TG crashed each and every time after 5 to 10 frames, no matter what I did. I paused the preview, I restarted TG, I even restarted Windows and didn't touch anything but TG's render button. No chance.
So I deleted most everything in the scene and rendered the splashes separately, and comped them in later.