My scrawl reads:
There have been many different postulations about the nature of dragon fire, even lightning and acid. I have not as yet read nor seen anything about killing frost, aside from magic. Furthermore, there are historically few ice-dwelling or themed dragons, aside for a few notable exceptions.
While I don’t have a reasonable biological explanation for ice breath (even if it were possible to make liquid hydrogen inside a living creature, I doubt you could store it), I can at least theorize about an ice dragon’s physicality.
The compact shape might not be right- I wanted a burrower. But long legs might be better for keeping the core out of snowdrifts.
The sail might need to be taller, like Dimetrodon‘s.