I'm really glad you found it useful! As for your questions; yeah, the federation file is supposed to list all the accounts that you want to modify; in the case of a custom attribute, I'm afraid you need to modify the python script in order to take that into account. It's pretty simple in fact: add another field in the federation file with the data you need and change the python script to read from that attribute.

IMHO it's mandatory and fun to experiment as much as possible but I think it's probably better to study and try to use computer science fundamentals such as algorithms, data structures, and design patterns more than just try out technologies. In the long run, this enables us to develop and understand any language.