I'm fairly new here and to the program. I too well understand the Jekyll and Hyde persona. Unfortunatly I was already deep in love with my addicted other and pregnant with his child before I found out what he was like when pain meds and Valium were around. It was much later before the drinking showed up. However, interesting to me looking back is how the Jekyll and Hyde showed up even when he wasn't activly drinking or using. It seemed to be part of his personality.
You have to make the right decision for you, if you see the problem is there right from the start you know its going to be there later too. You must decide if this relationship is going to be good for you. You sound like you have a good head on your shoulders. Good luck to you...Teggie