Part of the problem is that your son may not have any interest in listening to YOU. Perhaps, at a deep level, he does not respect you. Because he has become very interested in porn, it may be the case that he has an overall lack of respect for women in general.

It might be a good idea to locate a very strong-willed dominant male to become a central figure in your son's life. I'm pretty sure your son will respond to the right guidance and direction if it comes from the right source.