70C is where the FX-8350 CPU starts to regulate itself so that it won't burn up. Depending on how hot it actually got it might have done some damage but there is no means to really know for sure.
There are many issues that can cause a PC to freeze. I typically start troubleshooting by running Memtest 86+ overnight to check for RAM errors. You should also check the core temp of the CPU under heavy load to make sure it is below 61.1C according to AMD. Next would be to check the CPU vcore to see if it's in the normal range at light and under heavy loads. The applet OCCT will record the voltages and temps while stress testing the system.
Building a reliable PC involves more than just assembling the parts. You need to be able to configure all of the BIOS settings appropriately. This can be quite involved and frustrating as it can require a lot of trial and error with stress testing. It is however often the only means to get a 100% reliable PC.