Im in Middle tn with a Hoss 400 HE with a 400 gallon tank , the weather has been crazy , week ago in the 7o's and then been iced in last 3 days with nothing above freezing ,going to melt today !!
Im with Scott on its not the gallons , if its burning that much wood the heat is going somewhere , either the home or lost enroute underground, I heat 2 large greenhouses that are not insulated at all ( 6 mil plastic) that i keep at 58 degrees, when its at freezing i get about a 8 hour burn time on a load of wood , when its 5 degrees out I get less ,
as suggested id check what the temp is leaving the boiler , check the temp at your heat source at the house and them check the temp on returning to the boiler
wood makes all the difference, while mine will burn anything green and wet it also has a hard time with it maintaining temp with wet wood ,
if you got that unit for a golf cart you got a steal ! . I think your off to a good start and are way ahead of the game with what you have in it It just needs some fine tuning ,there are lots of good people here that will help you out but i don't think you need to give up and get rid of it
post some more details around what your settings are/differential is , but measure that temp at those locations and eliminate the piping underground losing it
I had problems with mine this year with it getting plugged up a bit , i thought it was clean by punching it out and i could run a stick down it and thought it was good , i had to buy a brush and modify it to fit the chimney so it takes 2 brushes to clean mine real good right ,
keep posting and asking the guys here questions, they will help you get to the bottom of it