Moving forward let’s try to post in the topics that relate to your questions so we don’t double post:
Since we currently don’t have a feature that limits joining a meeting with the same unique join_url there is no perfect way to accomplish this. Bad users will always be able to change the url or share the password and join_url. So unless you enforce users to be logged in with Zoom to join via the Zoom Native Client there, like I said there is no perfect solution.