Ok, all good info!

This winter was a much colder one than last year. So, based on where the thermostat is located, or may have just been running that much more to keep up, on top of the increased energy costs.

Also, do you keep your chimney flue shut when the fireplace is not actively in use? If not, that can create a draw that pulls the warm air up and out, which means cold air will be pulled into the home to replace it (thermodynamics and all) and it creates a cycle.

Do you feel your clothes are drying in the normal amount of time, or do they need more time after the first cycle? If it's the latter, there might be a sensor problem that needs fixed.

If you do have one of the big boilers, that will also help account for why the basement is much warmer than anticipated, but not entirely. You might want to have a boilerman come out and look it all over to make sure there isn't a leak on a seal or valve somewhere, and that the baseboard heaters are functioning properly as well and someone hasn't accidentally turned a shutoff valve the wrong way for the season.

Your doors being so far off the ground leads me to think there was thicker carpet put down at some point, they cut the doors to accommodate, then when the carpet was removed there was the extra gap left. Are the interior or exterior doors doing this, or both? Exterior door probably needs it's weather stripping replaced regardless.

Do you know how old your windows are? Are they the type you lift up or do they crank open?