Do a CPU LOAD test and see whether CPU-Z shows 4.5Ghz.

To be able to see your CPU operating at the desired frequency (4.5GHz in your case), change your power plan to "High Performance":
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Use CPU-Z to to check your CPU frequency.
Use Core Temp to monitor your CPU core temperatures.
Alternatively, HWInfo64 can be used to monitor both CPU speed and temperatures etc.
Download links available in the top post of this thread.

System crashing has many possibilities, check the BSOD message.
It could be due to overheat, wrong BIOS settings or insufficient voltages (vCore, vDIMM, VCCIO, VCCSA etc).
Most probably is insufficient vCore that feeds voltage to the CPU.
I saw your're using Load-line Calibration (LLC) level 4, which could cause too much vDroop (load vCore is too low). Perhaps you should try the lower level to reduce vDroop, best would be level 1 (minimum vDroop).
If LLC level 1 still crashing, then you should increase your vCore, notch by notch until your system is fully stable.

Easy right? Haha you're welcome bro
Btw, CPU-Z is not a CPU stressing tool, not even a good software for benchmark.
Run Prime95, LinX, OCCT (these 3 very stressful and too hot), AIDA64 Stability Test (less stressful), XTU, Realbench, etc.