Stupidity: Ashley Judd finally tracks her husband down and what does she do? She doesn't try to capture him to prove her innocence, she doesn't notify the police, she doesn't take his picture and send it to every police dept in the US, she doesn't even follow him to find out where her son is. Instead all she does is ask for her kid back. What was she going to do even if she got him back? She is still on the run from the law, with little money and resources and she doesn't even know if her kid even remembers her.
Stupidity: It is pretty silly for Martin Lawrence to go undercover as a police officer when it would make way more sense to go undercover as a janitor/custodian since his main goal is to gain access to the vent. A janitor would be a way less conspicuous disguise than a detective and slipping through a backdoor entrance disguised as a janitor should not be all that complicated for someone as savvy as Myles. But of course this would make a far less entertaining film.
Suggested correction: As you said, she's on the run from the law. Why would she call the cops and risk going back to prison and losing her son again? Even if her husband was alive, she has no way of knowing what will happen to her. This was her best shot (especially in her mind) to getting her son back, thinking her husband would rather give up the boy's location rather than die; whereas height keep the boy's location a secret if all he was facing was possible jail time, if that.