If he hasn't established his parental rights, he need to file a Petition to Establish Paternity. He needs to do this ASAP before his girlfriend establishes residency for the child in another state. Consult with and retain an experienced family law attorney in the Ft. Pierce area. I wish you the best of luck.
As Mr. McGinn pointed out, he has no legal rights until there is a final judgment of paternity. Once parental rights are established, a parenting plan will be established. That said, not a great chance of having mother and child return to Florida unless she chooses to do so.