RE: Running in sub-zero temps?
I wouldn't do it.
Not for any fear for the engine. With the proper preparations and precautions the engine will do fine.
No, I wouldn't do it because I don't like the cold - and you will get cold doing it.
There's a reason I moved from Minnesota to the deep south. In thirty years it's only gotten into the teens a few times and into the single digits only one time that I can remember.