A cpu passing stress tests doesn't make it 100% stable. I've been able to pass lengthy prime95 blend tests that complete all the FFT's. Then crash when barely doing anything, just web browsing. The reason was because the voltage was too low for lower clock speeds and idle. So I had to make some adjustments to Load Line Calibration and offset volts. Also, you can pass all those tests and some games are just a bugger for it, as you have seen
Simply trying to boot into a Linux installation is a good test for stability. If you can do it without problems then it's a good sign. My OC that I thought was perfectly stable for a long time just wouldn't boot into Ubuntu without messing up. Never gave me any trouble on Windows though!