Question about resist reduction

Hello everyone! There’s been a question in my mind for some time and it’s really bugging me: How do resist reductions work? More specifically how do they scale? Now I know for certain that %reduction scales with flat resistance reduction, but how about, let’s say, %elemental reduction and %fire resist reduction, or flat elemental resist and flat total resist reduction? Do these scale? Also if you have a couple of skills that reduce a particular %resistance, do they all stack, or only the skill with the highest resist reduction works?
I’m asking this because my char is a Purifier and has a bunch of skills and devotions which all reduce resistances but I don’t know if they all stack, or what… Currently I have these skills which reduce resistances (both percentage and flat):

Aura of Censure: 35% elemental reduction
Viper (devotion): 20% elemental reduction
Thermite Mine: 32% fire and lightning reduction
Eldritch Fire (devotion): 23% fire and 35% chaos reduction
Ignaffar’s Combustion (relic): 10% chaos and 10% elemental reduction
Elemental Storm (Devotion): 32 flat elemental reduction
Agonizing flames: 15 flat total resist reduction

Can somebody explain, because I’m getting dizzy from all of this. :rolleyes:
Thanks in advance!

Thank you, that was most helpful!