Lexie's right, and my take away from what she is saying is that you don't need to get diverted by all these details. If your 16 year old son doesn't want to be with him then, at 16, his wishes should be given some weight.
My situation was similar in that my daughter couldn't stand her father when she was 16, and my focus, at that point, was to try and guide my daughter toward an adult relationship with her dad. One where I wouldn't need to step in and mediate. Counseling and Alanon were both a great help to her.
I'll keep you and your son in my thoughts.