Blackcat,
I'm afraid my experience is exactly what you are trying to avoid.
When I did that kind of stuff (but not nearly as extreme), my answer was a very big pack. I used a standard Duluth.
The answer to the boot problem was (always has been, still is) is mukluks. I've never used them on dry ground. I carried them in the pack until we got into the snow. I've seen the Canadian Forces version on sale surplus, and I think they have a tread and can be used off snow. That might give you an answer.
The sleeping bag was the old Black's Icelandic, built for the Canadian Arctic Survey. It consisted of inner and outer (differentially cut) down bags that could be used separately or together. It also had a separate down hood, a large, heavy canvas cover and a large bulky egg crate open cell foam pad. They were intended for dog sled transport. These were extremely bulky (I rarely used the whole outfit) and are no longer available, but one can still assemble something more practical using that idea.
There's still a whole lot of bulk involved. The real expert on these questions is Phat, one of our moderators. He is currently familiar with the conditions you are describing. I believe he deals with the weight/bulk issue by using a pulk (a kind of runnerless sled). With a little bit of luck, he may come on and give you the real answers.
best, jcp