I have an obsessive personality too so I understand where you're coming from. I do however believe this to be an infatuation. A lot of what you write is cyclical - you say you want to know him more, then you make suppositions about his nature and why you would be good together and then you reaffirm you don't really know each other. It follows an 'obsessive' pattern. I would like to go back to what you wrote quite early on - you said he was taken. Surely you can see that your chances are practically non-existent? Perhaps that's fanning the flames the most, we all want what is unobtainable.

To quote St. Spock;

"After a time, you may find that having is not so pleasing a thing after all as wanting. It is not logical, but it is often true."

I don't believe in soul mates or just one person out there who is 'perfect' for you. Highly illogical. No relationships are perfect, i'm sure that even if you were with this man his physicality wouldn't be enough to detract from his worse points. The statistical likelihood of you finding someone who's better suited is good. I think a healthy dose of perspective is needed the most. Allow yourself to feel attracted to him, in time it may well pass, but be mindful that you're in 'love' with an image of him - one that likely doesn't exist in reality. It is ok to feel this way. Practically speaking he is also involved with someone else but you know he isn't the last of his kind. I think there is hope to be found in the latter.