The only thing I know is that he was born between jan1965-aug 1967

With a closed adoption, and you not being either the adoptivee or the birthparent, you only real chance is to register on reunion websites (a couple are listed in the sticky at the top of the adoption page) or to hire a private detective.

Records from the 60s are generally closed, and nearly impossible to open unless there is a medical emergency.

I hope you have found him and I'm sorry I don't have an answer.