I'm sure there will be some others that can help you with that questions. I've never been in that cold of weather. (nor do I want to be) I know how vg is thick and can get even thicker in the cold so I would recommend adding a bit of Everclear (Pure Grain Alcohol) to your topper or bottle of juice. Just my . I look forward to others helping you so I will learn something new also. I'd also get some of these for various locations.
I live in these temperatures. I'm from Nordic ancestry though, so I'm kinda built for it.
In regards to the juice. I'm not really sure if it will in fact freeze. I've had bottles sit in the mailbox all day in -30 and just be a little thicker than normal. I always order 50-50 pg/vg juice. I'd imagine if you kept it close to your body that would help. Someone with more chemistry knowledge would probably be more of a help, sorry.
Good luck with whatever they have you doing up there, stay warm and safe.
Oh and get some acrylic or plastic mouthpieces for your gear... metal ones will try to take your lips off with it. Don't make the same mistake I did lol.