The error was linux-based and not amikit.
I assumed the installation would take place on the usb stick, instead it was on the amipupsave.4fs file it created when I shut down the computer and with it the amipup session. It asked me if I wanted to create a save file for storing the changes I did and I said yes. AmiKit wanted to use that same file for installing AmiKit and since that file was 512mb it was too small for the installation to succed. That's why I got the errors I guess?
Now I resized the amipupsave.4fs file to 2,5gb and it installed great.
Even Sudoku ran without the AHI error I got before.
Jan/AmiKit, now I have another question: is Amikit meant to install on the usb stick? And how do I do that?
Thanks & greets,