Need help understanding family law in MN

No he cant unless there is another to take his place.

I have to agree with califdad.
Firstly-your boyfriend IS the legal father, the biological father is only a biological father and nothing more.

First, how sure are you of your facts? Did you get these facts solely from your boyfriend? I ask because your facts don't make full sense.

For example. it is unlikely your boyfriend adopted the child. It is unlikely a court would grant an adoption to someone not married to the mother. What is more likely is that he signed an acknowledgement of paternity. And that is why he is paying child support, because he IS the legal father.

Also, how do you know he is NOT the bio father? Has a paternity test ever been done? Have you seen the results of such a test if one was done?

But to answer your question, no, he can't give up his rights and no he can't get out of paying support. The only way he can get out of paying support is if he can prove he is not the bio father and MN law allows for him to challenge paternity at this late date. Or, if someone really adopts the child.

Correct.
Minnesota Statutes 259.22 PETITION.
Subd. 2.Persons who may be adopted.

No petition for adoption shall be filed unless the person sought to be adopted has been placed by the commissioner of human services, the commissioner's agent, or a licensed child-placing agency. The provisions of this subdivision shall not apply if:

(1) the person to be adopted is over 14 years of age;

(2) the child is sought to be adopted by an individual who is related to the child, as defined by section 245A.02, subdivision 13;/see below/

(3) the child has been lawfully placed under the laws of another state while the child and petitioner resided in that other state;

(4) the court waives the requirement of this subdivision in the best interests of the child or petitioners, provided that the adoption does not involve a placement as defined in section 259.21, subdivision 8; or

(5) the child has been lawfully placed under section 259.47.
245A.02,Subd. 13.Individual who is related.

"Individual who is related" means a spouse, a parent, a natural or adopted child or stepchild, a stepparent, a stepbrother, a stepsister, a niece, a nephew, an adoptive parent, a grandparent, a sibling, an aunt, an uncle, or a legal guardian.

As GV70 posted, that law would seem to preclude him adopting the child. So, if he told you that he adopted the child, he was either mistaken or not telling you the truth. Which then begs the question what else about what he has told is not accurate.

I'm not saying he lied to you. As you said; he was young and dumb, so may not have understood exactly what happened. But that means that before he tries to do anything, he needs to know what actually happened.