Why would assad use wmds when it only took a tall tale and innuendo to get Iraq invaded? The friends of Israel are the enemies of assad and his like, at least that's how he will be looking at it. Would it be worth risking the use of wmds for a battle against 200 when they're in a war against thousands, I'm guessing.
I suppose if they had his lair surrounded or something, maybe then.
but why would he risk geting the US and Israel involved? Jordan too maybe? That's occupation time and he knows it. Regime change for sure.