Thats how a computer program does Typecasting, that is what you are going to do.
The only thing is when its typecasted to int, its decimal aspect is cut off.
You should have no trouble making an Int = to a double in a trigger
As for your breath effect, did you use Freezing Breath or Frost Breath? Freezing is the one that freezes buildings, frost is the one that slows buildings. Frost Breath is raelly just an attack attachment. So you need to apply AOE to your tower.
Go to the unit, and scroll to Combat - Attack # - Area of Effect (full to small) and change those numbers to non zeros. Make sure that Full > Medium > small or there willbe bugs.
Then under Combat - Weapon Type, change that variable to Missile(splash).
If your tower is a single shooter, take the Frost Attack effect from the Black Citadel/Nerubian Tower and use that.