Good stuff. Nutty cold here in Sioux Falls right now. This is as cold as it typically gets. I grew up in ND and lived in Duluth, so this is nothing, but still.....
I would think plugging into 120v is the right thing to do, not to mention you could then precondition before leaving to go anywhere saving some battery juice. May not gain any range, but worth it just for those reasons I'd think. You hit up the Worthington charger? Working fine?