This is 29 days old and no one has answered? Hmmmm maybe its simple but # 2 is one of the things on my list that I have been trying to figure out for a few days.
For the local ui, you can create and manage the admin user from settings: Hub Login Security - Hubitat Documentation
Keep in mind the local account is different from your portal account. It is used only to secure the local ui, the portal account is used for everything else (linking Alexa, Google Home, logging into portal etc)
I was into the local hub security but didn’t want to add a user there without knowing if that was the best way. I don’t have any local security enabled so I didn’t want to start something I couldn’t undo.