Ok so,
Yesterday I tried this: -dx9 -usecoherent -ignorecoherentgpucrash -log which was @SoftFootpaws.9134 suggestion. It did work util I went to bed.
So, in order: I played for an hour or so with windowed screen, and then the PC collapsed. Then, I edited the direct access as per softfoorpaws recommendation and could play for like two more hours in fullscreen mode.
Today the game PC died within the first 10-15 minutes; I did tried @VaegaVic.6394 recommendation, lowered the FPS down to 30 (because it was already fixed at 60), used less than native resolution. PC collapsed within 5 minutes.
I don't know what else to do, my GPU and CPU are less than a year, cooling system is brand new, I can play other newer games at maximum without hassle; so I'm pretty sure keep changing parts cant be the only way ...
Tomorrow Ill try to tweak again my CPU / MB settings.
Sad part is, because yestarday I could play a lot, I was confident about finding the root cause and my 15 minutes of live today were used to get all the expansions, and then, crashed. I hate murphy's law.
If aynone elses have another idea, I'll try it.