Actually two very different questions:

A simple one: Crusade GA points are satisfied by capturing the obejctive province (both land and castle), is that right? And these can only be scored once, on the other hand you need not keep the provinces?

A complex one: I would like to know a little bit more about trade modell. If I have a resource how much do I gain and from which provinces? All that don't have that or those belonging to such faction that doesn't have that? Is it worth to establish a monopoly? How do I do that? E.g. getting Africa will do? Or if I have all provinces that have trade goods, that would be the ideal trade-wise?
Please enlighten me! ;)