I really don‘t think that Syria is directly supporting the insurgency in Iraq. Historically, relations between the Ba‘athist in Syria and those in Iraq have not been friendly. Syria, for example, supported Iran in the 80-88 war.
Furthermore the President of Syria, Bashir Al-Assad is western educated, and prior to the death of Basil (thought to possibly be the handy work of a certain intellegence agency that celebrates Passover), had no other desire than to be an opthamologist.
There are 300,000+ Palestinians in refugee camps in Syria. Only 90,000 are in UNWRA camps. The majority of these Palestinans come from population centres that are now inside of Israel proper. These Palestinians supported Saddam Hussien because of his record vis-a-vis Israel.
Most of the other camps are run by the PLO, Hamas, and Islamic Jihad to name a few. This population contributes to a major destabilizing factor in Syria, as many of them are near major cities, with a strong posibility of uprisings should it be publicized that the Syrian goverment is conducting relations that are not seen to be in the intrest of Palestinians, major uprisings could be a possibility.
I think that Al-Assad is simply allowing those militants who wish to fight in Iraq, to leave Syria. It is far more politically expediant to have the Americans deal with them than the Syrians.
As for the claim that Iraqi chemical and biological weapons, were on 45 minute stand-by for use, that would necessitate that the be deployed. Given that the US forces have not found anything substantial to date. (If they had Rumsfeld would have trotted them out by now). Leads me to believe that, Lieutenant Colonel Al-Dabbagh, is telling a certain friendly neighbourhood intellegence agency what they want to hear.