Kallskalt Pass is a dangerous place, and you get that across very well. The Howler Bear encounter sounds chilling and horrifying as it should!
I think that this scenario would benefit from a map that provided more flexibility and made clearer the goal is to get through it. Ultimately, by the end this gets lost in the trying not to freeze to death.
The opening sounds like a great encounter with the Steppe Wolves, but it also feels like a railroad. Player agency takes a back seat, which can be fine at times, but here there are catastrophic consequences for an action the players have no part in choosing. Even a bad choice where both situations have consequences would alleviate this feel. Like you can go around the lake, but it will double the number of wolves chasing you or something. Getting across the lake, will lose the wolves, but it is dangerous in its own right.
A lot of this adventure is dedicated to the freezing mechanics, so I understand the desire to ensure that at least one player is facing imminent death from freezing. Perhaps an alternative way to gain the freezing condition could alleviate this like spending too much time without shelter, and going around the lake pushes you toward the required time. And maybe the wolves attacks damage winter clothing making the situation worse?
The firestarting rules are pretty concrete and I love the beckoning snow maiden. Good stuff there.
This is a really punishing adventure. To offset this, there should be ample rewards. Maybe someone the players can save to gain something? Or a treasure trove behind the Howler Bear made from all the people it has killed up to this point. The Heavy Armor is good, but even that is damaged.
I had a phase in my DM career where I had a tendency to focus on the negative consequences of everything, which can create really compelling stories and verisimilitude, but I had to learn you also have to focus on the positive consequences, which I don't think comes as naturally. If you give a carrot, then you can get away with much more devastating sticks.