2) How is the regime going to deliver them? With artillery, they probably would only get one shell off. Bio weapons do not even have an immediate effect. They may use a drone sprayer. Plus, they don't think we're watching? Moving these munitions into position would be problematic. If they're in barrels, they have to either go in artillery shells or some other delivery means. If we see these goons loading shells with material from 55 gallon drum like containers, what do you think the coalition forces are going to do?
3) The Combat troops are slightly to the West of Baghdad. The prevailing winds may blow the attack back on the attacker.
4) It would totally justify the coalition's reasons for going to war.