Some quick thoughts, although I don't know the area, expected temps or potential weather changes:
- No overbag - the bivy will extend the temp of your bag and you always have insulated clothing to wear or put over your bag if temps realy fall.
- One stove with appropriate pot - I always have some food / snacks that don't require cooking in the event of a stove failure. Can you have fires where you're going?
- One pad - not knowing your winter sleep system, but.....can the blue foam pieces be used as additional ground insulation, you're insulated clothing could be used as emergency or additional ground insulation.
That should be good for 3 -4 pounds.
I don't see snowshoes on your list.