Sorry, I missed this.
There is nothing you can do with a stock 1070 that will break your video card. Try everything and see what happens. Just do not set afterburner to apply your overclock settings at login because it can create a boot loop if your GPU OC settings are out enough to cause a crash.
Pascal will down clock as temperatures increase. That is the nature of GPU Boost 3.0. If you are finding that the GPU will crash or give you watchdog Bluescreens of death, maybe have a look at tweaking motherboard voltages. A slight vcore voltage increase can someimes help and small Vccio and system agent voltage increased settings may also help with stability running the GPU faster.
I suggest that while high frequencies do relate to performance you look at primarily frame rates rather than maximum frequencies. You may find that in some cases, a slightly lower core clock with higher memory speeds give you better performance. You should also treat this as a performance journey, There are so many different variations that it is doubtful that anyone has actually found the absolute limit of what they can do. Next week or next month you may try something completely different and find a performance boost so dont give up trying new things.
I'm currently playing Metro Last Light and while in Fire Strike and Heaven is stable, in Metro doesn't. I did some test with the GPU fans at 100% and I can reach a higher oc, that's true. I'm still looking the best settings but the performance impact (even beign unstable) is not very noticeable (taking into account that I have an OCed card by default and I can reach +55 in core clock (without considering the curve) and +750-800 in mem clock).