What a fantastic mother you are to understand and accept that your child is a unique person on his own life path--not a carbon copy of you! It sounds as if he is fully confident in his freedom to explore his own mind and the world before him with all it's variety--no doubt due to unconditional love.
I would also highly recommend "The Celestine Prophecy" by James Redfield (mentioned earlier). It is written as fiction, but it is very good at showing that ALL people are connected. I believe that it was a critical turning point and a huge boost to my self-esteem and personal views about all humankind.
I guess my only 2 cents of advice is this--continue encouraging him to research and read about ALL cultures and religions, read (or at least peruse) the things he reads so that you can understand what he's read and ask questions about his viewpoints afterwards, and help him to realize that there are 2 sides to all issues (for example, the accuracy of the bible based on "the stories" being written down many YEARS after things happened).
I think it's great that you have such an open view to your child's willingness to develop spiritually. I am positive that my own lack of support at a similar age crushed me internally for many years. Many hugs to you and yours, and I'm looking forward to meeting you (and hopefully your son and the rest of your family) at the New England Apostafest.