Congrats on what sounds like a very successful cruise.
A couple of points responding to your questions:
1. Anything you plan to do on the boat that is labor intensive and can be put off until the mid point of your next planned cruise might be done more cheaply in Trinidad. Labor rates are a fraction of the US and the quality of work is very good. Example: dodger repair, painting, woodworking, cabin alterations, etc.
2. Boat insurance is expensive and some go without / self-insure. Question you have to ask is can you afford to lose the investment you have in the boat? If you can, you have a self-insurance option. If you can't, you should find a place in the budget for hull insurance.
3. Medical insurance is a different matter. If you're both young and healthy you might be inclined to take the risk. The low cost and generally good quality of routine and non-critical health care you can get in the Caribbean would also argue for self-insurance. The real risk you face is if you have a serious accident -- someone gets hit in the head with the boom which results in serious head trauma, or you're in a car accident while ashore somewhere and end up with broken bones and internal injuries. In these situations you may find yourself in a situation where you need to / want to come back to the US for care and/or recuperation. Without health insurance that will cover you in the US you're out of luck. There are health policies that will cover you outside the US and let you return should the need arise -- some require you to be outside the US for six months of each year. If I were you, I'd look into an option like that -- something that will allow cover treatment in foreign countries while you're traveling, but which will allow you to return to the US for if a major hospitalization is required or serious illness needs to be treated. You might try to keep costs down by accepting a high deductable where you pay the first $4-5,000. If nothing major goes wrong you'll end up paying very little beyond the insurance premiums. If disaster strikes, you can leave the boat and fly home for extended care and recuperation knowing that you're not destined for the poor house.