Re: your statement "contention that Hillary 'would erect a no-fly zone over Syria" (far from certain), presumably in contrast to Trump and his shiny promises of "safe zones":  Hillary said, at least twice, once during the last debate, that she would erect a no fly zone.  Was she "angling to start a war with Russia"?  Of course, not.  (So my premise isn't flawed.)  But she didn't see far enough down the road to that very real risk of war.  Too dangerous for the WH.  As for Trump:  he didn;t make a "shiny promise" about safe zones, though if he had, there is evidence that it could be done without risking war with Russia.  See Rojava.  See the difference?

You say I'm "making the fluid, byzantine dynamics in Syria too simple."  The fluid dynamics in Syria didn't prevent Rojava, which proves a safe zone to be a real possibility.  The dynamics of Syria do, however, strongly argue against a no-fly zone against Russian jets.  You still seem not to get the risk of doing that.