To me, the problem here is the large clear span - 30' and then trying to add a second floor on it. This is an engineering problem. As you go beyond 24 feet, the stresses increase dramatically. I actually have the same problem in that I want a 30 foot clear span and second floor living space above. I haven't gotten deep enough into it yet however.
It sounds like you need to be working with an engineer to determine all of the loads that will be applied, and how much load your frame can support. As is, it probably can't support both the snow and live loads of a second floor, as that is not what it was designed for. So then you have to look at what you can do to increase it's carrying capacity. That will mean moving bents closer together, reducing the width of bays to see if is sufficient to carry the loads. If that's not good, then increased timber size and careful analysis are in order. If it comes to that, your're then going to be building a frame from scratch.