I'm always interested to see the processing, moving, loading processes of others who are using this much wood. You're actually a bit ahead of me, I had been averaging 10 cords per season between two wood stoves, but have started scaling back on running the second stove. Hauling that much wood up a flight of stairs and thru a very long house gets tiring, after more than a decade of doing it, especially with knees complaining more each year from over-use/abuse. I assume you can load the boiler from outside or walk-out access to the firewood?
I believe I'm getting close to 60% of my heat from wood, but I don't keep enough data on electric usage to really nail that down. I know I use about 10 cords of hardwood + 1000 gallons of heating oil, and estimating these make about 60% and 30% of my total BTU's, with an approximate remainder of 10% being a few minisplit systems and random electric baseboards. My climate is milder, my average January lows are 2F above yours, but my space is larger and likely less efficient. I'm burning primarily red oak, the last several years, but now starting to get into some piles of shagbark hickory and ash collected in more recent years.