Good choice on the knife and saw for firewood. You could leave out your stove in forested areas which aren’t over-camped.
If the snow is deep enough, just bring cordage and small biners for attaching buried stick anchors.
Is the HG Burrow a quilt? It seems too light for something rated to zero. :) I don’t like using quilts below freezing unless I’m also using a bivy bag.
You might want a warmer hat for around camp below 20F.
Definitely add some type of waterproof/breathable glove or mitten shell, as well as a spare set of liner gloves and socks which you can hike in (not sure if the delicate P Down counts there). Without a shell, gloves are snow sponges. You’ll need a spare pare of liners while the other pair dries in your jacket or around the fire. I prefer wool military liners because they’re cheap and more fire-resistant.
Lithium headlamp batteries of course.
Those light wind/rain shells might be a bit delicate in some conditions–brush, falling on ice or into snow-covered debris.
I’m too skeptical of my ability to keep filters from freezing when temps are below freezing during the day. How will I know if the outside part of the filter away from my body freezes and cracks? I use either a Steripen or nothing in winter.
Add (maybe already in ditty bag):
compass
map in waterproof bag
sunglasses
whistle
backup firestarting method with emergency tinder
gaiters?
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