Ken,
I have been thinking about why your windmilling formulas were twice as high as code values, I think you are right that the exposure and location adjustments would make a big difference. And, it may have something to do with how wind speed is measured. Presumably, design of windmills is based on a steady wind speed, while design of structures is usually based on short-term wind gusts (higher values than sustained wind speeds).
I do not know much about the eurocodes, but it seems quite reasonable the same theory is used in developing the design pressures. For the most part in the US, simplified procedures in the building codes (There are charts for most residential buildings) are adequate for determining wind loads.
Cordially,
Joe