Adult adoption….for citizenship? Advice needed in VA

Location: Virginia and/or Arkansas ?

So my Fiance green card has expired due to his mom being a control freak that likes to drag her feet so she can run in and save the day! She’s toxic, anyway this happened cuz she said they would renew cards at the same time. We moved and she’s had “other priorities and been busy.” According to her, he’s got 3 years after the expiration to renew due to him being a “permanent resident”

Fiancé went to our local immigration office in VA…they told him he’s had too many extensions and renewals. Now Fiance is over 18 years old. His step dad wants to legal adopt him. He asked his wife several times when Fiance was a minor. She told him no. Now that Fiance is an adult step dad wants to adopt him for “inheritance” but says if this helps with keep Fiance in country that’s a really welcomed bonus. Step dad lives in AR.

Fiancé and I have a child together, second due in May 2025. I’d like to get the ball rolling on get this fixed or at least figure out how not to get him deported before I go into labor.

I guess the big question is how do I keep fiancé from getting deported while making him a US citizen.