I don't think you realize how big the earth is and how hard rock is. State sized chucks would have been ripped out of the crack, and they ended up a tiny fraction of the size because of the forces you are correctly saying they would be subject to. In a way, yes, they were turned into powder, but a human's size of power can get rather large when we are talking about earth's view of powder.
Also, you seem to still be claiming that asteroids and comets are (or, more frequently are) solid pieces? I'm pretty sure everything we've found so far is made up of smaller parts even if some are pretty big relative to others.
As far as small rocks bunching up together as they fly through space, I'm also pretty sure that's a feature of Dr. Brown's theory that in the absence of other gravity wells, close objects will bunch together just from the inverse square law which is why there are so many 'peanut' asteroids when they should have balled up if they are more than a few thousand years old. I remember a professor in college showing us the math on that disproved it was gravity of planets that was the mechanism by which astrology worked. Using the inverse square law he showed us the magnitudes greater gravity well affecting a child at birth from the ball of the ballpoint pen in the doctor's pocket than any planet or star, perhaps even including the sun although I don't remember that specifically. In other words, once all the powder pieces got far enough away from the earth, each other's gravity would seem, to them, relatively the only gravity wells affecting them in the whole universe.
And one more thing, once something gets ejected from earth, it's not only the amount of power it left with, but its trajectory that determines were it settles. I'm not an orbital scientist, but I'm sure they can do the math on what power and trajectory would be needed to get the asteroid belt and TNO's into the orbits they have today if they came from earth. If there is an orbital scientist that is available, I'd like to see what they say about the math. I think that would settle the question, and I'm certainly ready to agree with you if those calculations showed dubious numbers required to make it work.
Sure, it's not much, but the evidence available to claim a 360 day year before the flood is not pure speculation. Pure speculation would be saying the year was 10 days long before the flood.
Like I mentioned in a previous thread, an example of little evidence is not pure speculation: There was a show called Forensic Files where they go over cases where forensics made a difference in the case. In this show, there was a body recovered from the water when a boat that went through a storm needed rescuing. A survivor was also rescued who was the only other person on the boat when it left the dock. The dead body presented with a deep laceration in the skull. The survivor was accused of murder by the investigator. He claimed the injury was consistent with a large cutting tool found on fishing boats like this one and the man had confessed. The DA did not bring charges because he said the injury was also consistent with being hit by the prop and the confession was not admissible since it was obvious torture. Years later, with the advancement of forensic science, the truth was found out about which man was correct.
In both cases, both men had the same scant evidence. But neither was going off NO evidence. Let's say, for example, another investigator claimed they needed to find the closest beekeeper because he thinks the body died by massive bee-attack. Now that would be pure speculation with no evidence.
