The estimate you should use for this size house is about 100,000,000 BTUs.
I've seen a few fuel comparison calculators on the web and most use that figure, plus my house in Poughkeepsie, NY at roughly 2200 sqft uses slightly less than that for both hot water and heat. Maybe just for heat for your house maybe 80,000,000. (amazingly big numbers eh? Just think of that in calories if your trying to loose weight...makes a better case for cutting wood!
I know this is a coal related forum, but this company looks worthwhile http://www.woodboilers.com/