Unfortunately, I can't see any indications of what resources there are at any location, so this seems to mean I end up building my colonies "just anywhere". How can I find out what's there before building?
Press "H", it will remove all units and trees and you can see the terrain (note, you cannot see if the terrain has a bonus).
I never saw any such problem with Colonization. But like others I tend to stop trading via ships and use Custom Houses. When it is time to move your ship (any of them) can't you move it to a port yourself? (using the arrows).