I am very fond of my Dickenson furnace - much cheaper than any central heating system and toasty warm. I've had propane but now use diesel - super warm - and we added a valve interface so I can switch tanks in only seconds. each lasts so when I lived in Boston, we could heat the boat for probably no more than one or two hundred bucks for the winter.
To me, once the boat is warm, the moisture is not a problem. On the coldest days, I use a thin foam board insulation (very cheap) and set it into the areas against the hull - no more problems. Otherwise, I'm not really all that into adding insulation.
Best,
Mark N.
The Essentials of Living Aboard a Boat