Re: icy breath, my vote would be to hold off. I don't think it's quite there yet - in particular, Han's breath in the opening sequence with Chewie looks a little off - and even if it was, it seems like a world of pain to do that for every person in Hoth.
I also don't think the TIE fighter colors need to match throughout. I think it's perfectly sensible to allow for a "newer" TIE model to have been rolled out by the empire during the passage of time between ANH and ESB.