Where do millions of years fit into Genesis chronologically?

There are certainly those whose scientific knowledge is vastly superior to mine, who may be able to answer your questions better. But we should remember that the questions you've raised are very recent.

For thousands of years, the Genesis account was more than sufficient for Christians who accepted it as the inspired Word of God.

I feel quite strongly about one thing, and that is to always bear in mind what is the "dog" and what is the "tail." I fear that every time some new scientific theory comes along, some Christian scholars feel compelled to find some way to accommodate it. (Actually, this happens in virtually all the categories of academic pursuit. So we rush to justify "self esteem," to establish "boundaries," and so on.)

I don't personally need science to assure me of the trustworthiness of God's Word, nor has science ever dealt a death blow to my confidence in the Bible.

I can see how the "big bang theory" may be compatible with Scripture.

I can see many years could have occurred before Genesis 1:1 (Creation doesn't start with nothing, but with the cosmos in chaos), or even between 1:1 and 1:2.

It is not too difficult for me to conceive of the flood as producing the sedimentary layers, or for the world to have been created with apparent age.

But nothing I've ever seen or read has forced me to turn my back on the Bible as God's Word.

I think that when we get off into the scientific proofs we miss the point of the passage. In other words, what is Moses' (and thus God's) purpose in writing this text? One of the books that I would recommend is Sailhammer's book entitled (as I recall), The Pentateuch as Literature. We would do better to view the Pentateuch (and specifically the creation accounts) as literature than we would to attempt to understand them through a scientific grid.