Ben Levi,
1.) According to your “big animal before the Mabul” theory there should still be “Pre Cambrian rabbits” (maybe bigger ones- but they should still be there). According to your theory the fossil record still shouldn’t show many many generations of animals existing in completely seperate eras with some not coming onto the scene until much later then others it should show two groups only: one big and one small. This is all besides the points that there were plenty of small Dinos and other creatures in those eras, and the fossils are millions of years old.
2.) Similarities in body structure between people and animals may be discussed by some Torah sources a nested hierarchy isn’t.