sup..i can not make your estimate of your wood pellets come any where near heating your home. a search on the net tells me a ton of pellets is at best 14 million btu..a conservitive btu estimate for your home is 30 btu per square foot per hour (48,000 per hour for 1600 square feet) that makes 1,152,000 per day so if we even lowe that to 1,000,000 per day and say for average numbers only 100 days for a winter season we get 100,000,000 that would equate to about 6 cords of mixed hardwood (that would be about average i think for a home of your size)
now baack to your 2.5 tons of pellets =35 million btu or again on average about 35 days of winter?
could you have counted your pellet bgs wrong or use the space heatermore than you think
if you truly only used that small amount of pellets you will only use about 2 to 3 cords of wood. mixed hardwood would be close to 16 to 18 million btu per cord less the efficency rating of the boiler (lets say 15 million average) 3 cords would be 45 million less (again lets estimate) 20 percent for efficiency = 9 million off the 45 would be 36 million and that would equal your 2.5 tons of pellets
that is how i figure it..and i have been wrong before but it is something to think about