Welcome to the site Charlie.
Also, I welcome you to the group of old farm house owners.
For me, the biggest thing was sealing up the house. Everything in my 1886 farm house leaked air, not just the windows. To find out what else leaks, I highly suggest doing your own
home pressure test. This helped out a lot when I was looking for air leaks.
The next thing I would look into is closing off areas of your house that you don't need. 3200 sq/ft is a fair amount for 3 people. Closing off a room or two could really help out.
After that, I would perhaps kick the temp down a little bit. I run my house in the mid to high 60s. I don't know how your cohabitants feel about this, but it does save energy.
Other than that, I'm not sure how the heat pump disperses the heat through your house, but I've found (with my gas forced air system) that running ceiling fans helps out a ton to keep warm air mixed with the rest of the air in the room. The ceiling fan in my living room is pretty much going constantly all winter long just mixing air. If I don't do this, the ceiling gets 3 degrees F higher than chest level.
Thats all I got for now.