Richard,
I don't think you are a nutcase, although I wonder sometimes about those experts who do the studies. I have never seen a sea level projection that takes into account possible tectonic plate activity. Jamaica gets its share of quakes. Quakes have been known to lift an entire landmass.
The Earth is a dynamic planet in a dynamic solar system. I think it is a bit foolhardy to think that humans, as a species less than 100,000 years in existence can predict the distant future with anymore accuracy than we can predict the weather. Google predicted rain all day (80% chance of rain at 6am) but I went ahead and got a load of laundry done and line dried today!