The problems with your "math" begin with the use of a chemical WMD. No nation on earth has ever been able to deploy a weapon of that type with the effectiveness you attribute. Never in recorded history.
I'll also point out that when it comes to WMD's, there is nothing available to nations, let alone terrorists, that comes close to a Hiroshima type scale of carnage using chemical agents, let alone again what your "math" is indicating which dwarfs the bomb drops of August 1945.
I'm greatly concerned with the terrorist threat as it is based on facts. I expect us to be hit, if they have the capability, prior to the coming election cycle. The terrorists have misjudged Americans as badly, if not more so, than we misjudged them during the 1990's.
But wild eye'd claims based on faulty data isn't helpful. I won't even bother to dispute the number of terrorists you are projecting....just note there isn't a chemical weapon created at this time that would cause the carnage you suggest available to nations, let alone terrorists.
ok...lets try biological weapons. The method wasn't really the focus... the number are real...the math wasn't the problem...