None of this makes sense to me.
If the state was pressing charges how was his ex able to get them dropped? Did they not have any evidence other than her word?
How was he able to just sign his rights away. My understanding is that that isn't possible unless someone (like a step parent) is petitioning to adopt the child.
If you've never been convicted of a crime how in the world could it be used against you in any situation.
Jespah is right. You'll need a lawyer. A good one.
One thing they'll probably want to know is why you decided to have a kid with a man you thought was guilty of child molestation.