Some quick responses
3 - time works here, if you have a colony etc even out of your SoI, the situation will slowly improve. Think of it as the other states coming to accept your borish bad manners in taking something that was not originally yours ..
4 - CP and Military Control are separate items, if you can push CP to protectorate/colony status then you get the territory. But it often helps to take military control too as you can protect your buildings etc
5 - once you reach level 4 (ie the sail ships are obsolete), its a case of scrap and build (and pay the prestige price). The result is a very realistic portrayal of the chaos in naval design from say 1880 to 1910 (when everyone came to agree that the best design was an all big gun battleship and that other ships had to specialise around this). Its expensive and hard to keep up.
7 - not directly, but it may improve sales and usage of your commercial fleet - both indirectly may give you more buying and thus more capital
8 - tricky one. Best advice is to build up a large buffer but that can be hard in the 1880 scenario. Certainly don't build for a few turns and let the stock improve, then look at your trade pattern (this can see a lot of capital lost if you are not careful)
AJE The Hero, The Traitor and The Barbarian
PoN Manufacturing Italy; A clear bright sun
RoP The Mightiest Empires Fall
WIA Burning down the Houses; Wars in America; The Tea Wars