My ex-husband and I have been divorced for over seven years. Per our divorce papers we have joint custody and share financial responsibility 50/50. In reality he has never paid a single dollar toward the support of my son and has had very little involvement with him. He has made no attempt to contact me or my son for over two years. I am concerned that if anything ever happens to me, custody will automatically go to him because of the divorce papers. I would like to involuntarily terminate his parental rights so that I may choose a guardian for him upon making a will. I have very little money for a lawyer so I do not want to pursue this if it is not possible. Thank you.

I don't want to say its not possible, but it is highly unlikely. Unless he is a danger to the child then he is still his father, like it or not.

You can designate a guardian. No one is going to force custody on your ex if he doesn't want it. There is no "automatic" awarding of custody. But he IS the first in line if your assignment of guardianship were contested.

Paying support has no bearing on any of this, incidentally. I would go to court and have the custody arrangement modified though.