I need an unbiased opinion...what do you think about this email to an absent/deadbeat father.....?

I would say that your email is absolutely spot on. It tells it the way it is. You sound pretty magnanimous to this guy who's suddenly got paternal feelings while at the same time you aren't totally closing the door on him...which perhaps he deserves. I think your email will make him think twice and if he cares for his absent son, he will accept what you've said. I think you should save a copy of the father's email and this response to him for Gianni when he grows up and wants to know more detail about what has gone on between you and his biological father. This email shows you in a very favourable light indeed.