In Iowa you can't sign away your rights unless there is a person willing to except them.
Personally if this is the case, then leave well enough alone. Nothing else has to be done unless there comes a person into your lives that wants to take over parental responiblily ( adoption).
If you go to court and have it down in court you have full custody and placement of your child then they will make him pay child support. Once child support is started and you except any money its harder to get his rights removed, even if he wants them removed. They will probably still try to set up some kind of visitation. If he is paying child support he has rights to see his child. Once that is on paper no matter how much time has gone by if he changes his mind down the road and you refuse it could back fire on you.
I would leave it alone and let him go about his business if you can afford to to it on your own and you don't need to rely on his money. Then if he wants to see the baby and hasn't in months, let him take you to court and set up visitation. Then you can get the custody, placement and visits set up.
If down the road someone comes into your life and does want to adopt your child as his own it will also be easier on you to show this guy hasn't been in our lives in this long and it will be easier for his rights to be removed.
Good luck and congrats on your little one!