I'm two steps ahead.

First, I probably managed to find the right parameters for the EEPROM.
Probably because I could read plausible values but I could not write. Since my programmer can't write to this EEPROM either, it is defective and I had to exchange it for another one.
Unfortunately I don't have the right EEPROM and because of its age it is very difficult to get it. I have ordered some in China and it will take 4-6 weeks until they are here and until then I can only continue testing with a similar EEPROM.

Second, today I was able to prove that the Immobilizer off hack generally works.
But I still have to do some hardware and software development.

Take care of you and stay healthy.