I do not know the extent of your paleo-Hebrew language skills; I am not a Hebrew scholar. However, others who know more than I have commented on the verb conjugation in that sentence in Exodus and suggest that a closer rendering is "I will be who I will be." So unless you can provide a more ample description of the Hebrew grammar involved, this question remains unresolved. Despite that, the content of the statement is that of a simple tautology. As baseball players who lost say in interviews,"It is what it is." What does that mean? They have nothing more to say about the matter. And Yahweh had nothing more to say to Israel about his ontological nature.
As for the "grandfather" comment, I am not sure that you understood my point behind it. I am not calling Jesus "the grandson of God" but am suggesting that there is more to God than we have been told or probably even imagine. This relates back to the question of Genesis 1:1 and the scope of the Creation. A possibility is that shamayim and eretz in Gen. 1:1 is not intended to fit the modern cosmological model of the universe that is widely read back into Gen. 1:1. Perhaps the scope of the creation as intended by Genesis 1:1 is our galaxy, or our sector of the galaxy, or the solar system. These are possibilities but no further description is given that would allow us to determine more exactly the scope of Creation.