I feel you with the distance thing. My man and I are living apart, after living together for six years. I have been extremely cautious, if not down-right stubborn about not opening our relationship up. Due to all our work and school related stress the spark just isn't there between us and the thought of seeing him feel that for someone else makes me a little nautious, but when I remember how much joy we got from this before, I am reminded that I AM poly, and these feelings stem from something that is my problem, not his. So to get to the point, I really respect how comfortable you are with the thought of him having someone else to help him through you moving away. I just thought that was beautiful, and something for me to work up to.
Now on to your 16yo story. We ALWAYS check ids if people look younger than 25. It sounds crazy but we make em' show us their ids.