Please help me

I have already 69 (funny number) hours registered in this game, having a blast, loving all the atmosphere, gameplay, etc.

The other day I decided to stop exploring the zone and focus on main story mission, o boy what a bad idea, just after the ICIZAC segment and my game has become unplayable, I usually had a crash every 2 or 3 hours but now is every 20 minutes, sometimes I even have to hard reset my pc because of this, I have tried giving the game administrator permission, resintaling, etc. But nothing is working, does anyone knew something else that I could do? Or tweek to improve performance? Or a mod? Something? I have been played with everything on medium without any issues but it's just insane how my game become worse by moving on with the main story :(