If everything is working the battery temp should not go below 50F. When it's plugged into L2 it will cycle coolant though a 3 element heater that can go up to 900W along with any heat generated by the onboard charger.
The same is available while driving, so if it's really cold that heater can be running whether you want it to or not. That said, the motor does heat up during use and the car is smart enough to route that to the battery rather than running the heaters, so it shouldn't be too bad.
But for sure, plug it into L2 so the battery does not get too cold. Remote start to heat things up while it's still connected. If you go all out, you can pull enough to still drain the battery while it's plugged in. Warm up the seats, all that.
Once you're actually driving, set it to auto climate. I try to adjust it to whatever temp turns off the heat and doesn't cycle the AC on - and keep inching it down so long as I'm still comfortable. Doing that and substituting the heated seat for the heater as much as possible should give you as much as you can hope to get.
As Scottt asked, how much range are you trying to manage?
2012 Candy Blue FFE
33.5kWh battery pack
CHAdeMO DC Fast Charging