"There is a section of sandstone in the grand canyon called the Tapeats sandstone. This is dated
(by your people, not mine) at 500 million years.
But directly below that is a layer called Hakatai Shale. This is dated at 1.5 billion years old
Sure, the sediments were layed down. However, the time period we're talking about (between 1.5 and .5 billion years ago) marked the time when advancing seas put the entire region under water. Old, hardened sediments remained, but new ones were swept away. The advancing sea eroded away sediments. Eventually, the sea receded, and collections of new sediments could form with greater consitency.
"These lakes catastrophically broke through the Upwarp, and the Grand Canyon was cut out of solid rock by the drainage of these lakes through this breach in the dam."
Do you have any idea how big those lakes would have to be? Where were they? The size would have been immense.
"There could be an unknown princible which slowed down the speed of light after creation to the speed today."
That's not addressing the point. That's simple conjecture. There could be an unknown principle that allows ANYTHING to happen. Saying "Well sure there's no evidence for it, and no physical laws, but it could be" is not good enough. More importantly, light pouring in from distant galaxies (hence, older) display no variations from nearby observed light.
"God couldn't have created an expanding universe?"
The issue is, what hypothesis makes the most sense? Would God snap the universe into being in a state of expansion, with apparent remants of an explosion permeating the entire thing, or would that expansion trace back logically to an explosion? Expansion signifies momentum: that momentum had to come from somewhere. Saying "God did it" is too easy. What events in your life have defied the laws of physics? When has the sun stood still in the sky, as the Bible describes? (note: if that actually happened - the earth stopping its orbit - , the Earth would have fallen into the sun.)
"Well, the expolsion of fossils found in the Cambrian layer was a result of the great flood."
....and why don't we find any large, developed animals in the Cambrian rock? No humans, no horses, no whales? Could it be because they weren't around when the sediment was lain down?