Winter freeze out

It was a chilly day today. frost was on the ground early and as the sun shone, various patches began to melt. some road spots were slick with the shear frozen moisture. My new space heater was working awesome through the night. This drafty house I am renting is a wonderfully old carriage structure. a few weekends ago i sealed with shrink wrap most of the windows, some of which had 1/4 inch gaps that allowed a breeze, not a draft, of cold air in and most likely warm air out. the thermostat downstairs also has a gap in it, a temperature gap. It cannot decide if it wants the room to be a comfortable 65 or a hot 85. Seriously, it is a dial on the wall, I have a thermometer next to it, and it is just turned on to the first click, no where near the "comfort zone" on the dial. Due to this malfunction, last month's electric bill was $104!! Yikes, and the deep cold has not hit yet!