I've never been to Alaska, but here are thoughts from my lower 48 winter camping experience....

http://www.weather.com/weather/wxclimatology/monthly/graph/USAK0028?from=search

Average High: 33 F
Average Low: 18 F

I'd probably want a 0-10 F bag, even assuming I'm wearing much of my clothing. Plus, there's the psychological effect of Alaska just sounding cold!

Are your snow boots waterproof up to the ankle? There's bound to be some slushy snow and standing water and mud. Maybe a pair of rubber overboots would be a good idea--lightweight, and you can use your existing boots or shoes.

Water-repellant gaiters sound like a good idea to keep snow out.

I'd want thin polypropylene glove liners to wick away moisture, but that might reduce fine dexterity some compared to the contact gloves. A pair with the thumb and forefinger tips cut off might be helpful.