Hi OC, I couldn't help but migrate over here as well.
I'm actually very new to this debate online, but I have had strong feelings about it since I was young when I realized that you can't rely on the mystical and supernatural to get the changes you wish to see in the world. So why should you use the mystical and supernatural to explain the world? I have been learning all fields of science, and even though this debate is getting old real fast since it seems some people just aren't rational and rely on tactics rather than information, I see value in continuing since I am all the time searching into unknown areas of science and philosophy and becoming more well-rounded in any debate.
In response to your question about the heat contained in the Earth's core, there is actually a pseudo-reasonable response that a creationist could claim here. The heat that is left over from the accretion and frictional heat that resulted only accounts for a small portion of the heat inside the Earth (20%). The rest is radiogenic heat that is still being generated, thus balancing to some degree heat loss and heat generation. This is from the decay of radioactive isotopes.
There is a problem with this however. Of course 6000 years is not enough time to generate this heat. Also, the science used to predict the heat that is generated by the radioactive decay is the very same science that tells the Earth is old through radiometric dating.
Again, since a creationist's claim may be that we have this science wrong, they can simply twist this to say it produces more heat than we think and we have decay rates all wrong. If decay was much faster, dates would be placed older and more heat would be generated, thus explaining the hot core and a young Earth. However, it would also make nuclear power plants explode.
This is of course absurd, since we have a firm understanding of the heat that is generated due to radioactive decay and utilize these principles in generating nuclear power. There are many uses of radiometric decay that rely on a firm prediction of decay rates besides power generation as well.
As for the assertion that the Earth was obviously once entirely molten due to an exact composition such that heavier elements are closer to the center of the Earth, I think is all they have here is 'God did it.'
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