Comment about the Nordschliefe.
Just make sure you have insurance coverage when you go out there. Not for the fact that you may damage your car, but for the potential damage you may do to a biker or if you need to recovered to a hospital by air as you we involved in an accident.
Most Brits will not be covered as it is specifically excluded in the policies. I am lucky in Lux we are fully covered.
It is a fantastic road. I have done about 500 laps now (in various cars). If you get the chance do it. But do not gamble with it. It is narrow and it can bite you. The Abarth is a great car around the ring. I would suggest a dedicated track day if you do not have insurance. That way you are only going to have to worry about your losses and maybe a bit of Armco in the worst case scenario.
Also in relation to stickers... bad form to put them on a car that has not been round.
GREAT trip report BTW. Really enjoyed it