I removed the nvidia driver with DDU and installed a latter one. People claimed that this 347.52 is stable and does not have TDR. I did not have a TDR and a c0000005 error since then, but I guess it takes only more time to get the message. I installed the system with the BIOS having the old CPU microcodes and with a possible faulty SATA data cable, so there is a chance it is corrupted.
At last I found a test which indicates the problem with the nvidia and the usb drivers. So I don't have to play 24/7 to test the system, which was getting burdensome as I made the system more and more stable. Now it takes 6+ hours of gaming to produce a c0000005 error or several days browsing to get a TDR. I'll get my thermal paste, PSU tester, SATA cables, etc. this week. After that I start to try out possible solutions again.