It's not that temperature sensitive, 90C is plenty. If you can't keep the non-x3d processors underneath that you're just throwing away performance anyways
Are you? I'm pretty sure when I bought my 7800x3d, everybody was saying you had to be very careful about heat, because these damage more easily from high temperatures than regular CPUs. I just checked, and they do throttle at a lower temperature than others: 89 vs 95 degrees C.
It will still throttle itself so no real danger.
For performance reasons you need to be careful with heat on the X3Ds because it will throttle quicker (partially because of the lower limit, partially because the extra cache sits between the CPU and the cooler on that model making it harder to cool) but you don't have to worry about it from a damage perspective for the same reason: the limit is the point at which it'll drop performance to protect itself.
Yes, you are. They will turn off long before you can hurt them.