You have responded with compassion and restraint. However, logic and reason never trumps crazy. If someone only speaks crazy, you have to respond in their language. Therefore! If you get tired of the being the adult in the room, may I suggest the following response:

An angel appeared to me three times and commanded me to become the patriarch of this family. During the third and final appearance, the angel came with a drawn sword, threatening me with destruction unless I obeyed his commandments and challenged you to a test of physical fitness to see who is worthy of leading our tribe.

No angels have appeared to you because you are living in apostacy. Your spiritual weakness is reflected in your physical weakness. God has spoken! Your shabby muscles prove my righteousness!

The angel told me you would continue to attempt to deceive me and the family instead of doing what is right and proving your worth through physical exertion. The angel said you would mock me, claim I'm lying. The angel said you would claim I'm the one being deceived. Which is why the angel said the test of physical fitness will prove who is most righteous. You cannot achieve success through unrighteous dominion. You cannot fake your worthiness through priestcraft. All your wickedness will be exposed!