Yes, those ‘ISIS Russians’ are largely Chechens.
Russians don’t want/trust the U.S. to bomb Syria because Obama has repeatedly said he wants a ‘political solution’ in Syria meaning the removal of Assad for starters, not ISIS.
Obama arming the ‘rebels’ in Syria without articulating who exactly these elusive ‘rebels’ are has been insane. More so because allegiances in that part of the world change Very fast. One day a ‘rebel’ next an ISIS jihadi.
The situation in Syria is very unstable. For now, should Assad fall, Syria will go to ISIS, entirely.
I think it likely ISIS and Syria and Iran working with Russia and part of the same overall terror network that we were witnessing before the Soviet “collapse”. See Russian Roots of Terrorism (in bed with ISIS?) above.