You mentioned using the fireplace upstairs and a wood burner.
Is your wood burner an insert at the fireplace, or elsewhere?
Our house is about the same as you describe. We were remodeling for an extended period, so put a hand fed coal furnace in the back part of the basement. Then we added ductwork. Then more, and more, and more. Each one a patch until we had rooms finished enough for the radiant to be reinstalled to use the boiler.
You can "survive" this way, but it was NO fun
It is MUCH easier to run hot water lines to each zone through walls and floors than it is to retrofit a PROPER ductwork system in these old houses.
How comfortable are you with computers/software?
About how much is your electric heat run you for a heating season?