I think that both your description and analysis indicate that you have a really good handle on things. I agree that with sailing the exam often comes before the lesson. I think most experienced sailors (I have been doing it for 40+ years) can well remember such scary experiences.
I think your conclusions are valid. Perhaps your two biggest mistakes were not having the reefing gear setup beforehand (and not practicing with it) and trying to enter the inlet at the worst possible time. Were you listening to weather radio? Might they have had reports of advancing T-storms that would have given you more notice and time to duck into cover?
A bigger, heavier boat would be more comfotable in sich an experience but chances are you could still encounter slightly worse conditions in a bigger boat because you might push it harder and be a bit less careful. Buy a bigger boat if you want it and can afford it, but basically keep doing what you are doing - sail a lot and analyze your experiences.
Heading back to Lake Ontario for this summer. Relatively few stops along the way from Grenada. Martinique, Guadeloupe, St. Martin (must have something to do with the French food), then Bermuda, New England and up the Hudson/Erie Canal. We were going to go via Newfoundland and Labrador but June remembered that one of the kids is getting married this summer - details, details!