You cannot terminate a parent's rights until there is someone who will adopt that child. If there is someone who will adopt and there has been no contact for the period of time you state then you have a chance of termination. The fact that he is trying may create a challenge, but the bigger unstated matter is if there is someone who wants to adopt your son to step in his father's place.
THIS IS NOT LEGAL ADVISE SPECIFIC TO YOUR SITUATION. Answers provided here are general in nature and no one should rely on an answer provided here. You should always consult an attorney in person to determine your rights and what course of action you should pursue before doing so.