Your post went on, but most of it was based on this point that really should be addressed.The OP needs to think about the legal ramifications of her child having sex with an adult. ...
According to the OP, the son was 15 at conception and will be 16 at delivery. His girlfriend is currently 17 and will be 17 at delivery. She hasn't stated that the girlfriend was 17 at the time of conception. It is very likely that she was, in fact, 16 when they 'did the deed'. Last time I checked (and I admit that this issue hasn't been important to me for the last 26 years), it is not illegal for a 16 year old to have consensual sex with a 15 year old.
It should also be noted that many jurisdictions have qualifications in the law that would allow for a 17 year old (above the age of consent) to have sex with a 15 year old (below the age of consent) without being guilty of statutory rape (or whatever this crime is called in that jurisdiction). Based on the laws of the jurisdiction, these qualifications include, but are not limited to, both parties being minors, the individuals are close in age, or parentl consent is given. Yes, some states allow the parents to give consent. These states include Connecticut, Delaware, Idaho, Iowa, Massachusetts, Montana, South Carolina, Utah, Wyoming, and possibly others. Also, if the OP lived in Hawaii, this would all be moot since the age on consent there is 14.