Priests become Cardinals at piety 5, or from a Cathedral, but not a Huge Cathedral, 'tis a bug.

To stop spies, put spies of your own in there, it will get rid of them over time.

Merchants, get better with monoply of that type in the region (3 wines etc)
More money further away from capital, and even more if you have trade agreements with the Country that owns the region.

Send merchants to Timbuktu, and put them on the gold there. Lots of money!