Manufactured home is way too cold. Need help to cozy it up, please!?

This is a double-wide, 9 years old, well-maintained, in the northwoods of Wisconsin. I KNOW it is really cold, but this is just over the top. One end, especiallly, is almost impossible to get over 50 F. The furnace seems to be working, but am not sure thermostat is accurate. That is, it may be not kicking in when it should. Can anyone give me any hints as to how to warm it up? I do have a woodstove in the front room, and a fireplace in the back, but don't use the fireplace in back as too much heat goes up the chimney. Would an outside wood burning stove be worth looking into? This is uncomfortable, and I am not a wimpy person. Usually. I've got propane for fuel. Any help at all appreciated. BRRR!