Thanks for your comments and for bringing your Genesis interpretations to the table. I had not heard your interpretation of pre-existing matter before so that was something learned for me too.
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Wonderful questions! I'll take them one at a time.
0. If god didn't create absolutely everything, does that necessarily mean that he/she is not omnipotent?
That is such an interesting question. In the case of the version of the creation story as narrated in the NSRVue, we're only told about the state of the Chaos at the time that Yahweh began the act of creation. We're not told about how the Chaos was created, or by whom. So perhaps the Chaos just always existed, and after some period of time God decided he was bored with the Chaos and decided to create something more interesting. But it makes one wonder how the Chaos was originally created. If the Chaos was created by another set of beings prior to the time of the God of the Bible, then I think it's legitimate to wonder if the first set of beings had powers that were superior to those of God, and that God did not create the Chaos because he simply didn't have the power to do so. More on this possibility in what follows.
But another possibility is that the Chaos just always existed, perhaps prior to the time of the existence of God, and that God simply used the existing materials to fashion his universe. That interpretation doesn't necessarily imply that God is not omnipotent.
So I would have to say that the answer to your question is no.
1. Is it not possible for there to be more than one omnipotent being?
Following is a quotation from the Gnostic work "On the Origin Of The World," as rendered in English as part of the Nag Hamadi Library, Copyright 1977, E.J. Brill. (NOTE: I cite this passage not because I believe it to be true, but rather to demonstrate that there were many other perspectives on the creation of the world brewing at the time.)
Since everyone-- the gods of the world and men-- says that nothing has existed prior to Chaos, I shall demonstrate that [they] all erred, since they do not know the [structure] of Chaos and its root. Here [is the] demonstration:
If it is [agreed by] all men concerning [Chaos] that it is a darkness, then it is something derived from a shadow. It was called darkness.
But the shadow is something derived from a work existing from the beginning.
So it is obvious that it (the first work) existed before Chaos came into being, which followed after the first work.
Now let us enter into the truth, but also into the first work from whence Chaos came; and in this way the demonstration of truth will appear.
After the nature of the immortals was completed out of the boundless one, then a likeness called "Sophia" flowed out of Pistis.
And from there the story goes on to describe all manner of wondrous beings who prepared the way for the creation of Chaos. So there you have a tradition which clearly supports the existence of multiple beings who existed before the time of Yahweh in the Bible. Later, of course, Gnosticism was rejected by Christianity as heresy, so these ideas were by no means universally held.
There is also another Gnostic tradition concerning the god Yaldabaoth, who is described as an evil blind god who thought he was the real god. Here's short excerpt from the Hypostasis of the Archons:
And Zoe (Life), the daughter of Pistis Sophia, cried out and said to him, 'You are mistaken, Sakla!'-- for which the alternate name is Yaltabaoth. She breathed into his face, and her breath became a fiery angel for her; and that angel bound Yaldabaoth and cast him down into Tartaros below the Abyss.
...
"Now when Yaldabaoth saw him in this great splendor and at this height, he envied him; and the envy became an androgynous product; and this was the origin of Envy. And Envy engendered Death; and Death engendered his offspring and gave each of them charge of its heaven; and all the heavens of Chaos became full of their multitudes."
It's pretty confusing, but the gist seems to be that Yaldabaoth/Yaltabaoth thought he was a powerful being but was smacked down by Pistis Sophia, and his personal envy of others of the then existing spirits generated Envy, which in turn generated Death, which in turn infected the Chaos. And apparently all of this must have happened before the beginning of the creation narrative of the Bible.
So back to your question-- is it possible for there to be more than one omnipotent god? The word "omnipotent" implies the power to do anything, so it would appear to support the ability to create other omnipotent gods, just as you said. And would an omnipotent god have the ability to create another god that has the power to destroy the original god? Hmmm... seems pretty likely that would be a bad move for the original god.
On the other hand the notion of monotheism insists that there is only one god. That would seem to imply that the one god does not have the ability to create other omnipotent gods, in which case that one god is not really omnipotent. Or perhaps there is an additional necessary assumption about a single omnipotent god-- namely that he/she must necessarily be wise enough to avoid creating another omnipotent god, since that would most likely not end well for either of the gods.
The Russell Paradox concerned the set of all sets that are not members of themselves. You may have heard of this cast as a question about the barber who only shaves the faces of those who do not shave themselves. Question: Does the barber shave himself? Set theory had to adopt a rule to prevent such self-referential definitions of sets. It would seem that to make the concept of an omnipotent being work, there must be an additional constraint similar to that which was adopted to rule out the Russell Paradox.
The whole thing makes my head hurt. So I think it's easiest to just assume that the notion of a truly omnipotent god-- one that can create other equally powerful gods-- is just not plausible.
2. If there does exist an omnipotent entity then by definition it has the ability to destroy itself, to cease to be
Yes, clearly. It would be totally possible for such a being to decide that he/she is sick of it all and no longer wishes to live.
3. If there did exist multiple gods and if they displayed the envious, jealous traits that we read about god in the OT then would they not all vie for contention in regards to humans?
The God of the Bible is a jealous god: You shall have no other gods before me.
One would suppose that other gods who have the same jealous attitudes of God would do everything they could to get a corner on the adoration of the human masses. So yes-- it seems that such a circumstance would inevitably lead to conflict, if not all out war, between the gods. Not good.