"It's pretty clear that these are leftovers from the Iran-Iraq war. Even the Pentagon has conceded that they have exceeded their shelf life and although still dangerous, are no longer weapons-grade."

I don't think Saddam ever enen made what we call weapons-grade, but it's good enough to kill people- and better than you are going to find under the kitchen sink. So maybe a drop doesn't kill you, maybe it takes two drops. If one drop didn't kill 10 people, the US miltary might deem it pretty low quality. Considering that any chemical weapon is fairly useless to begin with- for US purposes- the US miltary could kill huge numbers people with strictly conventional weapons- but they want to win wars, not kill massive amounts of people.
Chemical weapons are pretty effective against trench warfare* and good if you want geniocide, or various type for non-lethal applications [tear gas or sleeping gas]. Saddam's chemical weapon were in the opposite of US smartbomb direction of focusing firepower on only those targets you want to take out. Saddam's main purpose of chemical weapons was to mostly kill non-soldiers- civilians and Iran "mass wave" charges of unskilled poorly equiped children.

*large scale trench warfare is as outdated as castles and horses. The methods and means are still used, but not as the Grand Plan. For example, control the skies is major part of modern war, as are fast assault and mobility on ground. But you still can use horses [afghanistan], and dig fox holes and sandbag reinforcement & and blast walls [or tunnels/caves with Vietcong/Bin Ladin].

" Santorum's posturing is just that. The best proof that there are no vast stockpiles of WMD's squirreled away in Iraq is that if there were, the insurgency would be incorporating them into their IEDs by now."

Santorum's purpose is posturing- if posturing includes bringing political attention to this issue. There could be several things Santorum wants to do, such as point out the recent wave of lies that Dems saying there was no WMD and therefore invasion of Iraq was mistake. {Whereas Bush would rather not re-fight this issue and doesn't want to re-focus the issue on this- because he making effort to get more international involvement. And Blair's argument [which Bush is trying to be supportive of] is to acknowledge the past disagreements but focus on what can be done now.}
And there is other things here, but politicans posture- what hell else do they do- really? The normal critism of posturing is "only posturing"- in other words not saying anything of any significance. You can't say that about Santorum- but you can say that about Dems- with their bug out to Okinawa silliness- everything the Dems are about lacks anything anyone reasonable could call substantive.

"I do agree (without proof, but with justifiable suspicion) with Tom's thesis about the possibility that much of the stockpiles were transported to Syria before the US invasion. If that's the case, look out if there's any regime change in Syria any time in the near future."

There is no international law preventing a country from having chemical or biological weapons. The only reason it was problem in regard Iraq was because Saddam signed a cease fire agreement which prohibted Iraq from having them {mainly because in past Saddam had used them- that use was a violation of international law}. We know that Syria has chemical and biological weapons. We also know Iran has them- it's not issue- unless they actually use them in a way which violates their international agreement.