The order requires him to pay support. HOwever, if he doesn't, you will have to take him to court to get him to pay. Then he can show he was living with the child and helping to pay household bills which is part of what child support is for.
I agree with the other attorney - you divorced him for a reason. Find another roomate!!!
I recommend that you talk to an attorney in your area.
You've lived with this guy before and you divorced him. Why would you want him back in the house? I don't know either of you so all I offer is -- ask yourself "why did I divorce him?"
I am not intending this to be legal advice, because I don't know the particulars of your situation. Call me if you would like to discuss this or other isues.