I'm not sure how to get a custom package onto the other nodes. In the snowflake case, I was able to use the azure cloud shell and run commands on all nodes to pip install it. In this case I'm not quite sure since its a custom package.
Yes, that is the to install it in all the nodes.
I am sorry, I am not a airflow expert, I don't know how to distribute this kind of packages.
I'd recommend you to consult in airflow forums about this topic. Then, if it is not a DAG deliverable mechanism we can help you on how to proceed in the nodes.