If I were a US President and really wanting to do something about the killing, etc. I believe I’d try for a coalition to partition off part of Syria, protect it with no-fly, no-incursion forces (a real coalition) and give (i.e., make) refugees a place to live safely. No emigration, no exodus, no new entitlement citizens in the west.
We could call it “Palestine.”
I would bomb that scumbag Assad into the dirt, and then bomb the new crew if they looked at me sideways. There ya’ have it: now the paleos (and the Russians) will call me a neocon.