Ok, lets see... your creature died from the cold due to its materials having the same colddam point as all other creatures. Add this:
[SELECT_MATERIAL:ALL]
[COLDDAM_POINT:NONE]
anywhere below the other material tags. You might also want to remove the leather material.
In the tissue section you are modifying a skin tissue, odd as your using scales instead of skin. You also dont need to select a tissue right after loading its template, it selects things it loads untill you load something else or put in creature tags.
As for the breath material, you probabaly dont need to make a seperate template. Best thing here would be to just use [MATERIAL:POISON] and put the stuff from the template below there, along with the syndrome. Also remove the extract tag from the material, this tag can cause tragedy for your merchants as it means they can bring the stuff in barrels. It explodes them as they enter the map.
The materials temperature is also below 0 kelvin, which might be the cause of some of your troubles. The minimum is somewhere around 9800, consult the wiki for the exact number.
As for some nitpicks, you can just leave out tags for strength properties, rotting, ignition temp, etc. None of these cever come up into gameplay with a material that only exists as a gas. You can also replace that huge list of [STATE_NAME:blabla with just one [STATE_NAME_ADJ:ALL:blabla]
EDIT: missed an obvious one, the material doesnt have a fixed temp. Its not cold.