I don't understand how anyone can get miles a day out of the simple problem of three thousand miles of distance covered in 4300 years.
Nobody does. Your fantasy doesn't incorporate miles per day, other YEC fantasies do. Waltie and Johnnie and many other YECs think all the continental movement happened during the fludde year.
Etewitness acciounts are certainly a lot more reliable than conjurings about the past from the present could possibly be
It's been proven, insofar as anything can be proven in science, that eyewitness accounts are unreliable.
But your claim that we cannot discover the past from the traces in the present is just an unsupported and disproven assertion.