You need to put him on notice that by the time he is able to develop trust and whatever seems to him to be missing from his life at its current stage, you might no longer be available due to having pursued other interests. The appreciation of this possibility seems to somehow be missing from the whole long account COMPLETELY, which seems so strange.

He is self-centered and out of touch with reality if he does not realize that it is not all about him and his feelings and whatever is in his mind - you might be gone for reasons that have absolutely nothing to do with his feelings and whatever it is that is in his mind.