A former agnostic, with doubts?

[Cyberman]

I don't like to get into the semantics of nothing used by some Atheist physicists because it is misleading because as you say it's always something.

Then bring something by Theist physicists and we'll examine that. Then perhaps explain why we are capitalising nouns in this way.

Theologians seem to be in agreement that there was no time before God's act of creation, since time began at that moment.

And they base this consensus on..? Not to mention the presupposition in your statement has not gone unnoticed.

If time was created by God, there is no before the act of creation. That makes God an ontological first cause, but it doesn't mean there was a time before creation. This was even discussed by old theologians prior to the big bang theory. Now if this is true, whatever first cause in creation that started the universe has no time to precede it. That being the case...why can't this cause be the first cause as it has no time to precede it without an ontological first cause of God?

If the scenario is defined in such a way as to render "God" as not unreasonable, then the answer to that question is along the lines of "there's no reason why it can't". However, if the only way to make this work is to define everything in its favour, then by all means knock yourself out; but don't go pretending there's any correlation with reality until you've established one.