You forget that God helped Noah. He could have easily shrunk the animals or not let them get hungry for a year, or, fed them animal manna. Plus, you're forgetting the miracle of holding a 450' wooden boat together without leaking. All proof that God can do anything.
But really now, if humans lived 900 plus years, what about the rodents? ( not to mention the insects and bacteria and fish) How many mice were on the planet? After all, there's some that think that even the animals were not allowed to eat meat in the beginning. So with no predators, what do you think? Maybe 100 or 200 year old mice that had like a billion babies? They must have been everywhere. Obviously, we must have piles and piles of bones from this time period. It was only 4000 to 6000 years ago. It must show substantial differences in structure and bone density wouldn't it. Oh, and those bones of the giants, the Nephilim. I saw their pictures on Youtube. What was there DNA like? Half human, half "sons of God"? They have run tests on them haven't they?