Angela says that Peter would have been alive if Nathan wouldn't have flown him up. Does that mean Peter could have died after falling towards the ground and splattering into pieces?

I think Angela was speaking out of her grief.
If Peter exploded (went nuclear) on the ground in NY City or in the air above it he still would have scattered pieces everywhere. Unless Angela was thinking of putting all the pieces back together like a puzzle I don't see how either place would make a difference.