I think you got some good points here, maybe some can be included ...
as for the cracking of ice sounds, here are some examples:
http://www.youtube.com/watch?v=RL3EjH9-WSs
http://www.youtube.com/watch?v=4eg-kK6FeRQ
http://www.youtube.com/watch?v=JR_jIJe0UY8
ok, it's more of a roaring like thunder, but with some tweaking one could build some acceptable effects ;-)