Wow. Sustained for the full hour? That's 7200kWh monthly. Roughly 2x per sqft compared to my 80's home.

I've spent a lot of time in my attic air sealing, distributing insulation that was poorly installed, installing new insulation, insulating the basement, air sealing the basement. In my experience, it did not lower my power usage but in that time I added a second heat pump so I can't compare apples to apples. I can anecdotally say the upstairs seems to retain its temperature better. I'm hoping this winter I'll know if it helped.

If you end up solving your problem blog about it and I'll read it...