Minus the legal issue, I have a friend in exactly the same situation.
Lived with a woman and her infant for 6 years, She taught the boy to call him daddy. then she wanted out of the relationship, suddenly he's not "Daddy" but "Rick", and he doesn't have a dad. Although she still accepts child support he offers, she doesn't cash the checks. Now she's moving from DC to Kentucky with the child, and he intends to follow leaving behind friends, career and school.
She isn't openly hostile, hasn't said don't follow us. Lets him see the kid.
So far my best advice to him has been, " I don't know, Rick. I think you're fucked."