How do I file for dissolution of parental rights on an absentee parent?

I have an 8 year old son who has a deadbeat biological father who has not been in his life for 7 years. There is a child support order established since then, I have received minor payments (i.e. $80 two or three times a year at the completely most, the latest payment being made today after a year for $36) and would like for him to be stripped of any parental rights he may have. Besides being irresponsible he is unstable and has never wantd to make contact with my child. i have contacted him a few times and every time he has given me a boo hoo story about how things are going for him. I'm about to get married to a wonderful man who has raised my child for the last five years. My son does not know any other than him as his dad. Upon getting married he would like to adopt my son. Does anyone know how to go about this?