If you have the son in custody GET A LAWYER NOW!
No matter what the cost, you will save money in the end otherwise you will be paying support and keeping your son too.She will have to forfeit any back support too.If you really want to see your son like you said, then get custody and you can collect welfare or whatever it takes to keep him.
Stop making excuses and take charge of the situation or you will be paying your X for years to come and she will make you miserable.You can do this if it is what you really want.Get help from family,friends or welfare, ANYTHING.