Try this . . Take a propane torch and heat the crank snout to about 175° or so. LET IT COOL. Put on your puller, apply a little tension.
Then take a can of "Air" and cool the damper. The expansion of the previous heating and then cooling of both pieces will cause them to "Shrink" slightly away from each other, and if you just keep tension on your puller, it ought to come off fairly easily.
A word of advice about the "Fire Scissors" or the Rosebud. When heating a piece of metal, whether it's Iron or Aluminum or anything in between, anything over about 200° of heat applied to metal is just a waste of BTUs unless you're gonna cut it off. 90% of the expansion of a metal object is achieved at that temperature. Anything more will generally affect the hardness or temper of the metal.
And, generally, if you have to heat it to loosen it, it needs to be cool to touch before you start twisting on it with a wrench or other device. You expand it and then shrink it. That's the loosening process.