And on this note, Good night!!!
OK
How about a FBD for each of the sun and moon orbiting above the flat earth?
Answer that,
Are you stupid or have never taken physics?
You want me to create one free body diagram that has 3 object in it. What college did you attend?
By definition a Free Body Diagram has ONLY 1 object and all forces that act upon that object.
Ooh, we are getting

touchy aren't we!

Do I have to translate simple English for you now, guess you skipped
Reading Comprehension 101!
No I am not stupid, I asked you for "a FBD
for each of the sun and moon orbiting above the flat earth".
Now, "a FBD for each" means
one FBD for each, that is a
number of separate Free Body Diagrams.
I was not expecting the earth as well, because that depends too much on which one of the numerous flat earth models you subscribe to.
So present me with a FBD for the sun circling above the flat earth.
This must show the forces on the sun allowing it to maintain its (unknown) height and causing it to travel in its weird spiralling motion.
Then do the same for the moon.
Just remember that according the this Flat Earth Society the sun and moon are each about 50 km in diameter and about 5000 km high.
Now, how about it!
PS We know how those things work on the
Heliocentric Globe! You see we have a model that works, you don't.