The Maritimes/Atlantic provinces could very well stay part of Canada.
Look at Alaska and Hawaii. They are hundreds of miles off the continent and they remain part of the U.S.
Saint Pierre & Miquelon is thousand of miles (km) off France and it remains part of France.
Rev: I don't think the changes will be as complex as you predict.
Trade: Quebec major partner is the New England (84% of exports from Quebec). The New England customers have chosen Quebec, not because we are smart or nice and clean, but because we have the products they need at a price they are willing to pay. Quebec has some very good cards in his hand to keep dealing with New England (they need our electricity.)
Currency: The ROC would most likely want (if not need to) Quebec to keep the $CAN as the local currency. Any country would hurt badly economically if they were to loose 25% of its GDP and population resulting from the split and international traders would most likely shy away from the $CAN, resulting in a very sharp decline in value for the $CAN on international markets.
Labrador: I don't think Quebec will ever try to re-open the Labrador territorial dispute.
IJC: As Quebec would own a fairly large span of water bordering the ROC, I think Quebec would become de-facto a IJC member.
Quebec borders: What we have is what we get. International laws are very clear on this issue.
Quebec (as a province) does not sell electricity to the U.S. and Ontario. The sales contract is with Hydro-Quebec, a crown corporation. These contracts do not need to be re-negotiated and I doubt very much the U.S. (new England states) would walk away from it in the event of a separation of Quebec. They need it and for the time being, have very few alternatives unless they built new power generating stations (coal, oil, or nuclear).
This has not been widely publicized, but back in 1994-1995, prior to the last referendum, a lot of preparation work had been done with several foreign countries (including the U.S.) and world organizations (UN, World Bank, NORAD,) and in preparation for a successful referendum. Complex financial and political arrangements had been put together to be able to react to possible catastrophic scenarios the day after the referendum.
The Separation is not only a dream, it had to be a well thought and planned business, social, international venture where experts in various fields have put a lot of work and have looked at many angles.