If he has not had contact with the child in over a year, and you have not received child support in the same time period you can file for TPR under abandonment.
In most states child support is still considered a form of contact and seen as the parent contributing to the child's life.
If there is currently no contact and little child support, would it perhaps be in the best interest of the situation to let sleeping dogs lie, so to speak? Does your ex have a history of documented violence? You could seek a TPR based on that as well if that is the case.
If the child support is a high amount you may be able to get your ex to sign over his rights in order to relieve his financial duties to the child.
Stepparent Adoption Blog