I will give you as much info as I can. Others can help on some other areas.
1) First, on the taxes, I cannot help you at all. I am not Canadian. You should speak to some of your brotheren up there. There are many on this board. I cannot remember, but Faster may be Canadian and I think he spends the summers in the islands. Give him a shot there.
2) Boat Insurance. As far as the boat insurance... there are several options depending upon location. For Florida and Bahamas, you really should consider Boat US. To the best of my knowledge, it is not US citizen restricted. The basic policy will cover you east of the Mississippi up to around SC or NC I think. It will not cover the Bahamas. $100 more for Bahamas for the year. If you plan on heading further south to the winwards (or Cuba) you will need to pick up seperate riders from other companies. You may not want Boat US at all. It may be tricky even for a Canadian to get a rider for Cuba... but as a US citizen, this is hear-say so I will not comment further.
3) Hurricanes. You need to decide where you will weather Hurricanes. Many companies will not let you weather winward south and have stiff requirements for coverage during the hurricane months. Again, using Boat US as an option, if you are in FL during the Hurricane months your insurance will be quite high. 250-300k on my boat was 4200/year in FL. If I move my boat west of the Mississippi, it droped in half. I think the same holds true for moving up north but I have no experience up there. As I recall, it is SC/NC north... but those rules seem to change a bit and Boat US will help you with that. I like Boat US because you can change midseason without redoing all your insurance. Basically just given them a call and it is done and they will credit/debit you for your change of location. However, as I said before, there can be issues with the south islands and NO Cuba (which may not be on your venue anyways).
4) Medical Insurance. That is a personal decision. Check with Cam or others. You will probably not want the "doctor visit" level, but you would probably want Evac level. You may need a special rider for a medical evac to a supporting country where you will want advanced medical care (like the US). There are horror stories about people having insurance, needing to be evac'd to the US for advanced care, and getting whopped with a bill that goes well into the tens of tens of thousands... and your medical insurance does not cover that.
5) Bahamas. Here is your entry regulations for the Bahamas. Bahamas really caters to boaters. You could spend three years there and still not see everything. We met a couple in the Tortugas once that told us about some Candadian friends they found in the Bahamas that were going to just stop off there on their way south... and 15 years later were still there. Anyways, here you go: http://www.bahamas.com/bahamas/about...=24465&level=2
6) Florida cruising. Hmm. Well, if the Bahamas caters to boaters, Florida caters to money. It is changing, and many of the places that you could anchor before are either being taken up by commercial developments or over run with mooring balls. (It is a sensitive subject for me... and others). The east coast is very pretty but more developed. The west caost is very nice and more laid back. The keys are nice, but getting very developed. Marathon is nice and an easy run. If you do that, take the time to jump about 60-70 miles west of Key West to the Dry Tortugas. Plan on spending as much time as you can there. It is BEAUTIFUL, great diving and reefs, lots of wildlife including sea turtles and ship wrecks to explore, an awesome mid-1800's fort with the cannons still sitting there... etc. It is a National Park and out of the way... but worth it. From there you can make your way north up the FL coast where there are still many places to anchor and feel a little secluded. If you plan your trip right, you could make your way all the west to Texas over the Hurricane months and have very nice marinas, cheap insurance, and cheap slips. Texas to Florida is about 5-7 days at sea or quite a bit longer if you hug the coast. From Texas you can pop south down Mexico and around the Yucatan.
There, that is a lot of information to absorb. Others can help more. Cam is very knowledgeable, but a US Citizen so cannot answer everything. Faster and othes can help a bunch too. Good luck, keep in touch with us.