My views on objective morality

[Mystic]

Double implications exist.

A -> B
B -> A
Therefore A <->B. 

It's not circular reasoning. It's that both imply one another.

If there existed a child, there existed a parent.
If there existed a parent, there existed a child.

That's a double implication in the definition of child and parent.

The same can be true of morality because of it's relationship to God as the source.

Where do you get this stuff?

child <-> parent isn't an implication or a mutually supporting idea.  It's a definition of those terms.  "Parent" means "someone with a child" and "child" means "someone with a parent."

If you define morality as "whatever God wants us to do," then God, if real, proves the existence of morals.  But that would be a poor definition of morality.
If you define God as "whoever/whatever made morals possible," then morals, if real, prove the existence of God.  But that would be a poor definition of God.

This is the thing. How do we define God? God means a being Worthy of Worship. This includes moral excellence, not just being ultra powerful.

Also, the link between the will of the heavens with of the earth, with morality seems to be quite common in cultures in how they defined morality.

Part of the definition of God is whoever/whatever made morals possible or the only being which morals are possible through. It's not a poor part of the description of God and in fact also points to the totality of his names and aspects, and is one of God's all-beautiful names.