Whether the father can be convicted of statutory rape is a criminal law question. I am not a criminal lawyer. So, I cannot advise you on that issue.
On the family law part of this, the answer is clear that you need a lawyer to help you navigate this situation. It is clear that this is a complex case and you are conflicted about it. YOu really need to sit down with someone to discuss it at length.
Your son was born out of statutory rape. You always and still do have the option to file a report with the law enforcement agency where the statutory rape took place, that agency will investigate and present the case to the district attorney to accept or decline prosecution. Your not reporting the incident and about your age will be taken into consideration. Its possible that the lawyer you believe ignored this fact actually fully understood this and felt it may not be an avenue to pursue at this time.
for your sake and the best interest of your son, it is imperative that you consult with a family lawyer about your options.