So, I've been gone a efw days now... Long story short, massive hardware glitching.
The important, rendering-related part is solved, for now, after 2 format sessions, and a fresh, brand new, windows 10 installation. Before that, Iray would crash down even on the simplest cube scene test, even if geometry, textures and materials wouldn't even reach 200 Mbytes combined. Just trying to render, with some 10 Mbytes geometry, and some 5 Mbytes textures would crash down.
Now, it seems stable (Will try a real scene render later to confirm this), but, the catch is that my motherboard is gonna die soon. the audio chip is half fried, and, inevitably, it WILL affect the system as a whole. In the meantime, my rendering will be slow, super slow in pace, as I'll probably have to focus more in fixing my machine than rendering.