Your settings are isolated to your logged in user so are already protected by virtue of the fact that you need to be logged in as a specific user to view and change their settings.

If someone else logs into the machine, they will not be able to see your configuration settings, each user gets their own settings and their own service instance. You can use shared-user mode to allow all machine logins to access the same configuration, so locking down would not make sense here.

Only an admin user would be able to stop the service, that's because they are an admin and their level of access will be honored.

Can you provide an example of why exactly you would need to password protect access to the software from users on the same machine?