Is this a question?
The B4J code sends the messages once.
You shoudn't use the console at all.
Not sure what you are talking about. There is no server involved. The B4J code which you can call from B4A as well sends the message to Firebase servers.
If you are using B4A v8+ then you should call Service.StopAutomaticNotification. Otherwise you will get two notifications in Android 8+.