What about the impossibility of the size of the dinosaurs, with 1G gravity? Is the expanding Earth a good explanation?

This is a misunderstanding and a misinterpretation of the fossil record and the geo-physical history of the planet as a whole. These giant beings did, in fact, exist and they existed in the 1G environment you know today. So they were not a relic of an earlier era with a micro-world that somehow expanded to its present size and configuration. They were able to do what they did because of the energetics of their beings. If you think about this, there are examples of animals here today that defy reason from a human perspective. If you look at the squirrel, who can spend all day running up and down trees, defying gravity, moving its body adroitly hither and there and everywhere, with extreme energy reserves that seem inexhaustible—a level of physical activity far beyond the most developed human athlete. Animals that can swim vast distances with few interruptions, birds that can fly across oceans without stopping, animals and insects that do something similar, with the tiniest of muscles, but can fly vast distances with seemingly inexhaustible energy capabilities. This is what allowed these gigantic organisms to move about. They had a different type of energetics in their make-up, in their architecture, in the way their limbs moved, and their body moved. This is because of creation, not because of evolution. It was an idea appropriate to those life forms but not needed in other settings with organisms of a modern sort. The need for human to have a nest that would be safe, created the need for a balance in nature so humans could survive and defend themselves, if need be, from other creatures looking for food. There was an entire reworking of life on the planet, multiple times through the ages. There were differing needs for this. There were times when humanity was present, but annihilated through extraterrestrial intervention, and then humanity was restarted once again. The historical epoch of the age of the dinosaurs, and the larger than life plant species, and gigantic insects were owing to differing physiology, and chemistry, and biological form, than are used today. Things have been reworked and re-engineered and re-geared to be human scale, and the reason is, specifically, to provide a world for divine human to inhabit where they would truly be the dominant species, and truly have control of things, and as was stated in early writings, the intention to have dominion over their world. That was the reason things were created anew in differing forms. So this is an astute observation by people who understand the improbability of such large scale beings, but they are extrapolating from current biology in coming to the conclusion such animals would be impossible. The conclusion is correct—that such beings could not function based on current physiology and anatomy. There is something missing here, and it is not geo-physical, it is biological and physiological, and so, it is simply a nice hypothesis that is drawing the wrong conclusion.