don't agree with your opinions on this Teribus, there are far too many negatives as far as Russia is concerned and far too few positives.
The regime does not require chemicals to win or even shorten the war.

The perception that President Assad authorised the attack has turned world opinion against him.....when even the US were saying that there was no way forward without him.
The attack achieved nothing militarily, eighty women and children killed, the Americans killed over a hundred in Mosel with one drone strike.
"People saw planes dropping bombs containing Sarin gas"....and how did they know the bombs contained Sarin?.....both the regime and Russia have stated that an attack took place(using conventional weapons) and one of these rockets/bombs struck a cache of gas which the Russians say had been deliberately left to provide the conclusion we see before us; the planes would in that case still be seen dropping bombs, but the gas would not have been contained within them.

To say that Assad gassed women and children because he "thought he could get away with it", does not make good military sense and if the Russians were involved they were bound to take into account world opinion in the aftermath.