1) There has been and is a regime sectarianisation plan. It was there from 20012 when the shabihia hundrrds of killed men and women in an attempt to make it a a sectarian war - the easier for the regime to sell itself.
Regime thugs attacked anyone who protested the regime regardless of sectarian affiliation - so you can say the regime turned the revolt into a war (there were armed groups right from the beginning mind), but can you deny that it was the opposition who turned the war into a sectarian war? What happened in 2012 (and earlier) was a growing dominance among the opposition of a theme about the regime being a case of Alawite oppression of Sunnis, this later got served up by various secular liberal/nationalist/leftist allies of the Muslim Brotherhood (and other now "moderate" islamists) in a more palatable form for Western audiences. I don't remember anybody talking about the regime being a case of minority sect rule or about the regime's sectarian strategies in 2011, I remember prominent Alawites coming out against the regime and there were no shortage of Shabiha and killings in 2011.
There is nothing inevitable about the sectarian degeneration of the revolt and nothing inevitable about the regimes strategies succeeding (if you genuinely think there was some sort of sectarian strategy). And so regardless of whether there was some (cryptic?) sectarian plot being pushed by Assad, the writer you promote is still deflecting the essential business of critiquing the revolt onto a quick and easy "lets blame Assad for the sectarian nature of the conflict".
Regarding the figures - there are no reliable figures for who is killing more civilians, not even any rough approximations. More to the point why are you asking? What do you hope to prove with such figures? That the armed revolt only kill tens of thousands of civilians? What is the maximum amount of blood shed by these groups before they cease to be the lesser evil? Is that a sensible question? Besides the evil of the regime is not solely measured in terms of its conduct during the civil war and neither is the evil of the opposition regime to follow it.