Hunt NH... Prayer was sent for you buddy! I think that's a wonderful thing you are doing. Just stick with it and ask for God's guidance from Him. He will help you with what to say, when to say it and how to say it. Too many times, when I'm witnessing, even on here, I say things that come out wrong or confusing. Talk to God and ask Him to help you through the whole ordeal. One thing that I think is 100% true is that you were meant to be the 1 person in this guy's life to speak to him about God.
DON'T GIVE UP! Trust in the Lord your God.