~ I've been looking at a pellet stove, the house even has a place where a wood heater used to be, ...
This means that if your pellet stove could keep up, and it can, that your best case savings are 200$ a month.
It sounds like your house has no duct work so any force air solution is out.
If one of your goals
IS A/C, then I would go with a couple of mini-split units. Sure on the days when it is below zero, you will have to "augment" your heat, either with you current electric heat or a pellet stove. Check pricing at Lowes/Home Depot/Tractor Supply or even local hardware stores.
No question a pellet stove is your cheapest solution and I would install it first, before doing a mini-split install. It is also a great backup if/when you have a power outage. Forget coal. Too messy/dirty. Pellets are clean and good quality hardwood pellets leave very little ash.
That $200/month saving is not out of line. Buy good quality pellets, store them in a dry area, preferably off the ground. Yes, on really cold days you may have to feed the stove 2 - 4 times. Use the heat pump when the outside temp is above 0F.
Start shopping for a pellet stove NOW ! There is still a lot of winter left !!