Dr. Craig is a liar.

[SteveII]

On the A theory, once God created space-time, God underwent an extrinsic change with the new relationship to his creation and in doing so became temporal.

A truly timeless entity cannot do anything, including creating space-time. There is no moment of "change" without some form of time. Without change, there can be no cause and effect. God cannot exist sans universe, then suddenly create the universe absent some form of time to which he himself must be subjected to. You're addressing what happened after God created space-time without addressing how God  could have logically created space-time absent any form of time or change.

Why can't a timeless entity do anything? Even a series of mental events is enough to form a before and after (therefore some measure of "time"). Why does causation need space-time to work? Further, why can't a cause can be simultaneous with its effect?

On the B theory, you could conclude that God did not undergo any temporal change (neither intrinsic nor extrinsic) and exists outside the block of time.

If the B-theory based on Relativity is correct, then all times past, present, and future have always co-existed and there would never be a moment where a creation event was required, which is why Craig dismisses the B-theory in order to hang on, however tentatively, to his precious Kalam. He would also adamantly disagree with you that God currently "exists outside the block of time," as Craig believes God is now definitely temporal post creation.

I don't think you are right about the B theory of time. You might not prefer to call it a beginning, but it will have a front edge. You still have cause and effect to measure a before and after all the way back to that front edge. I merely pointed out that if the B theory of time is correct, it would actually be a more simple relationship between God and time than on the A theory.