Is the glass cheaply made or what? I got a crack in mine a few months ago from a flying pebble too. I've never had a cracked windshield in any of my other cars.
When my car was new it did that. I would rev it in neutral so my friends could hear the exhaust and then afterwards it would sound like belt squealing for just a little bit. It must have went away because I haven't heard it in a long time.
It really is the baby whisperer! Valves open puts my little girl to sleep in no time. Something about the rumble. Like others have said, rear facing would be an issue but forward facing works just fine. Having 2 doors makes it a little more difficult to get her in and out but worth it for the car.