Many thanks for helping me out! However, the job isn't done yet...

First I send a mail to Blockchain.info support with all data I could provide them. Waiting for an answer.

Also I tried the trick of importing the aes backup file into the old version of Multibit. That succeeded and I see a notice 1 private key imported. But how can I get that private key on my screen to copy it and rush to my wallet to take the cash since 4 years?

Eric.