This illustrated tutorial has the answers to the three bulleted points in your question, but it doesn't answer the part of your question about about documentation for any of the Python code. Below is a screenshot of the gufw application from the default Ubuntu repositories that shows how easy it is to get the currently set rules in gufw. Gufw is a graphical front-end to ufw which is itself a front-end to iptables.

If you really want to get down to the code level with ufw, then you're ready to consider using iptables in order to get exactly what firewall rules you want by running commands in the terminal.