Yeah, you just have to exchange new Canadian bills at either the Cuban airport or a Cuban bank, there's nothing you can do before you get there. I always found there are english speaking tellers at the banks, and they go very slow, so there is no question about what they are doing. You cant bring any of it back with you, so exchange it back when you get to the airport.
Make sure to have a few bucks for the airport taxes (I think $20) when you leave.
Don't know about the private home licensing, never heard of that, could be true but ignored in the regions I was in, or maybe I did not notice.
Havana for a full week depends on you, I would enjoy it, but I can hang out at the same bar day after day too.
I only ever took buses, don't know about taxi scams. As I said before I have never had any issues.
Your questions are on the first page, I will reread them and see if I missed anything, lol. (RBC Card is fine, the main one that hangs people is American express, I think Citibank is a no go too.)