Haha that is not going to happen. The mounting system is very secure and it uses a backplate which strengthens the motherboard and keeps the cooler secure.
It could if the builder is a nub
Air cooling is not at all dangerous.
And the guy you're talking to IS the builder :)
Have you ever seen a heatsink fall off when screwed on? Or have you only read about it once in the thousands of various threads you've seen?