It might be best to reset to defaults, run it for a bit and see if you still get crashes. It's probably instability somewhere with your ram, cpu or gpu.
You have plenty of power so I don't think it's your psu, do you have the 4 pin cpu power cable connected? It's not mandatory but when overclocking extreme you want to have it connected.
You could reset the bios to defaults and enable xmp and run it like that for a while to see if it's a ram issue, if it seems ok then your cpu or gpu overclock is unstable.