Welcome to the forums Tolus Gallicus.
Firstly, I am not a developer of the mod, but I can answer your questions.

1. They swapped cultures to make it a bit easier. This will be definitely fixed in the latest port(I hope)
2. - need to check. I forgot -
3. You can't have new resources. You can only edit the existing resources.
The maximum number of hidden resources allowed is 64.
4. Hidden resources can't be described. Or do you mean something else?
5. Is it really necessary a Roman folder in the UI? UI means User Interface.

Hope it helps.