I figure the father was lucky in three ways. First, his daughter survived. Second, his warning shot didn't hit someone unintentionally. And third, he didn't shoot the BG (much as the BG deserved it), since the use of deadly force, while evidently justified, turns out to have been avoidable and might have jeopardized his freedom.
IMHO the warning shot was excessively dangerous and a poor choice, even allowing for the stress of the moment.
OTOH I agree completely that a parent's duty is to protect his or her children, regardless of what hairs the law may split about the use of deadly force. Protection of one's family is a higher obligation than what we owe to the statutes, if only because the family--not the city, state, or federal government--is the basic and most important unit of society.
Just my $0.02.