I don't know where that came from but it's NOT from the US Copyright Office website.
The first part was from the the copyright law FAQ (same site you posted) and involves the tests that a court will use to determine fair use. the case I referenced (if you read the decision), goes over the judges decision regarding each of the four categories and how he decided on each of those categories. The key is that it HAS to pass the four tests,
according to the judges interpretation of the circumstances, to be considered fair use. Semantics has nothing to do with it, if the judge determines it passes according to the guidelines, it's fair use.
I'd also advise you to read
Legalities 4: What is Work Made For Hire? | Owen, Wickersham & Erickson, P.C. regarding copyright ownership. Just because you snapped the shot doesn't automatically grant you a copyright. The real kicker under the "Work For Hire" clause is that the copyright act a "collective" work could be considered to be many things including magazine or other periodicals, newspapers, even catalogs, and advertisements. Whether the court would consider the OP's styling as "work for hire" would be an interesting defense.
The third paragraph has to do with bringing suit in general. In order to file suit against someone for a grievance you have to have "clean hands", you can't go into court demanding justice if, you haven't followed the letter of the law either, your case will be summarily dismissed. If the OP published a minor's image on social media without a release from the parents, then there are state and federal laws that come into play. No one can photograph or film your child in a location where he or she (or the parents) believes himself or herself to be safe from such an event without the express consent of the parents. This also brings up the second matter of "Standing" you have to be the aggrieved party when seeking damages. Whether the OP holds copyright or not, he
doesn't have a release, so he has no claim for damages. The person in the image has "standing" not the OP.
I'm not an attorney, do not claim to be one, and offer no legal advice, but over the years, I've been both plaintiff and defendant in enough high dollar case to know my way around a courtroom. As I stated before, other then sending take down notices, I would highly advise the OP to consult an attorney with experience in copyright violations to discuss the merits of his case, and the cost of proceeding to court, before making any rash decisions. The costs could outweigh the benefit and the last thing you want to do, is end up paying the defendants legal expense if the ruling goes horribly against you.