There is no new Creed. If it's not a faithful translation of what the Harps of the Spirit wrote at the first two Ecumenical Councils, it's not the Creed.
The anathema against Arius doesn't allow the wiggle room you're trying to use to have an 'earliest point "begotten" applies'. Arius's "there was when the Son was not" is heresy.
And no, God does not need to exist in time. Time is a created thing. Any appeal to physics is appealing to created things, which only by an improper analogy have any application to theology per se. Physics may have some relevance to economy, but not to theology.
Yes, there is. This link gives the new one, which is common and showed up ~1975. Here' one link, that shows what I should have seen, but saw the "new" version instead. The use of the word eternal is irrational, the use of "before all worlds" is not. Jesus was more than just capacity, which is all "eternal generation" could refer to. Generation is an action, which requires that it occur in time. The earliest time it could logically happen is by decision after the first ponderings of creation. There would be no logical reason to "generate" one's person, before they pondered doing so.
"Arius's "there was when the Son was not" is heresy. "
I don't know much at all about what Arius said, or the details. What I do know is that Arius claimed Jesus was a creation, which is wrong. Here's a link to what Arius said. "the Arian, though he did not come straight down from the Gnostic, pursued a line of argument and taught a view which the speculations of the Gnostic had made familiar. He described the Son as a second, or inferior God, standing midway between the First Cause and creatures;" This doen't even resemble what I said.
"And no, God does not need to exist in time. Time is a created thing."
Time in this world is a created thing. Time in God's Heaven is not created, nor is it the same thing. In order to exist at all, time is required. In order to use the word "eternal", time is required. In order to create, time is required. Just because no one can read God's clock does not mean it's not running.
"Any appeal to physics is appealing to created things, which only by an improper analogy have any application to theology per se."
If God is real, then their must be an underlying physics. It was known in the OT, that no one could see the Father, or they would die. That's, because of the physics. The Church fathers refer to the physics of God as "substance". If there's no substance, then there's nothing. The physics of this world are not to be mistaken as the physics of heaven. The physics of this world are represented by the cherubim waiving the flaming sword in Gen 3.
"Physics may have some relevance to economy, but not to theology. "
Physics has no relevance to economics, other than the intellectual conception and the phenomenas studied rely on the underlying physics to exist at all. The "physics" is the reality, not the math. The physics refers to the "substance", it's nature and interactions. The math applies to both. In the case of physics, it is physical theory. The theory is not the physics, it represents the physics.