I assume this piece was written before this afternoon's hearing at the Senate Armed Services committee. I thought Sec. Kerry, in his opening remarks, did a good job of filling out some of the gaps you mention.
I was surprised you didn't seem to think that the broad and obvious use of chemical weapons against a civilian population was, in itself, sufficient to justify a stiff military response. Allowing chemical weapons to go "mainstream" is not something I'd personally like to see happen.
Lastly, re. Hezbollah and Iran, the former had no real capacity to enter a conflict with the US (other than through terrorism), and the latter has no intention to give the US the slightest excuse to attack its nuclear installations, so there'll be lots of huffing and puffing but that's about it (IMO, of course :-).