I can help with only a couple of those items.

'v' is the hot key to see your trade routs. You cannot send troops to a province via sea if the faction you are attacking have any of their ships there, even if it's an ally like the British in your scenario. The money screen (little coins button) will tell you how much each province is generating from trade. You trade with nuetrals, I am not sure about enemies. A province must have a port to trade with you.