That understanding would make sense for v16, but it doesn't take v14 into account. A slightly more literal translation of v14 in the KJV according to Strong's is "and God said 'Let there exist' lights in the firmament..." The lights "made" in v16 can only have been "made" or "ordained to accomplish" what God wanted after they were created, or began existing, which v14 suggests happened two "days" after God saying "let there be light" in v3.
I understand that apparently elements are made in the nuclear process that goes on with stars, (which would include the sun,) (not that either of the 2 links you provided said anything about that) and that this process would account for how the earth got its iron core etc. Another possibility is that God made the earth with its iron and lava etc. before the sun was created (because He's God, and He's not bound by mans' understanding of science, and He can do that), and later on He made the sun.
I agree that the earth is older than 6000 years, but it's not just Christians, or Christian scientists who believe that it is only 6000 years old. 6000 years is simply a time period, for some event(s), believed by some people. I know some Jews who believe that the earth is 6000 years old. I know an agnostic who believes the earth is 6000 years old. Neither of these groups of people are Christian. The belief of some Christains that the earth is 6000 years old, or the belief of some Christians that the earth was created before the sun, doesn't indicate that all Christians believe those things, nor does it mean that all Christians are wrong.