At anchor there is a fan called the "endless breeze"--basically the same as the Fantastic fan, used in RV's--which is 12 volt powered and relitatively low amperage draw.
I have used both mesh screen on the outside (like Texiline), or shade mesh from the Home Depot type of store. On the inside, I use foil/bubble type of insullation, which substantially cuts down the sun temperature inside.
You should be able to retrofit an opening window. On the top, a 16" x 12" hatch may also help--but remember if you get a clear plexiglass unit, the sun will shine thru, and increase the heat. You can also made sun shades which go over the foredeck and side decks out of Sunbrella. The fore deck shades can have a rope down the center and attatch on the sides to the bow railings. Side shades, can use PVC pipe to hold them out and give visor effect.
I am sure we would all enjoy stories of your C Dory Cruising in Bermuda. We enjoyed several weeks there as we staged for our trans Atlantic passage in 1984.