Yeah I highly disagree with you on the Bolin romances, one was highly abusive and creepy (from Elsa toward Bolin), and the other Bolin was being stupidly opaque about his unwanted advances. I don't know about you but even as a teenager I understood when A) a relationship was bad for me and

when my 'moves' were unwanted. You also seem to forget fascism was in fact a revolutionary middle-class movement to oust the traditional authoritarian aristocrat from there power base , not a reactionary conservative movement we see it as today. I think the parallels are pretty clear. It's nationalistic movement to unite the 'nation', the ideals of this nation embodied in a charismatic leader, and the threat of violence to all who oppose them. If she was an analogue to a Russian revolutionary she'd either be a communist or a person who advocates democratizes or at least so form of republic (from the October and February revolutions respectfully) and I think it's pretty clear she's neither of those things, she's to nationalistic and power hunger to be so. Thus Bolin is a analogue to those famous browncoats who decided it was a good idea to burn down the beer hall in Munich. It's is parallel to the Third Reich, or Mussolini's Italy, or Franco's Spain in it's politics and social movements. As for Kuvira being grey or black I direct you to this image:
That's from the first episode. You could argue that they simply reused characters model but I think the guys and girls on the show are smarter than that. If those two people are the same then Kuvira isn't just declining to help feed soon-to-be starving people, she's using people she captured and then with the threat of death made them vow themselves to her to actively deny soon-to-be-starving people food so they have no other choice but join her. That shit is black as tar.
Other than that I really can't refute your last point. I just think Mako is more a man of order than he is analytically realist and you'd think Bolin learned his lesson last time with Varrick who is also attached to Kuvira. It's seems to be a character regression of Bolin exploring already explored territory.