EDP throttling results in a limited frequency. This problem may have recently got worse.
At the beginning of the log file you posted, it shows constant EDP throttling even when your computer is idle. You should never be seeing EDP throttling during an idle situation. After a while EDP throttling magically goes away. At that point your laptop starts to limit the CPU multiplier to as low as 8 which reduces the CPU speed to approximately 800 MHz.
It is typical of the Dell Latitude series that when one throttling method does not work, a laptop will automatically switch to a different method. The amount of throttling depends on load and likely feedback from a temperature sensor on the motherboard. The CPU temperature does not seem to be what triggers the random throttling.
The box to the right of PowerCut shows Enabled in your screenshot so that is working correctly. When running a benchmark with PowerCut enabled you might have noticed that the power consumption being reported was very low. This can solve one throttling problem but it does not solve the EDP throttling problem that you have.
Did you check the Disable Chipset Throttle box in the Options window? This can be used to solve another throttling method that only Dell laptops seem to use but it still does not solve the EDP throttling issue.
Some Dell laptop throttling issues are caused by the power adapter. Are you using an original Dell OEM power adapter with the correct power wattage? If your laptop is using a generic power adapter or if your laptop fails to detect that you are using the correct Dell adapter, the BIOS can decide to set a low current limit. This can cause EDP throttling.
The Dell website shows both a 180W power adapter and a 130W power adapter is available for the Latitude E6540. It is quite possible that your laptop limits the current and CPU speed when using the 130W adapter. The 180W adapter might fix your EDP throttling problem but there are no guarantees. I am guessing that your laptop originally shipped with the 130W adapter.
https://www.dell.com/en-ca/shop/pfydresults/234759?categoryId=8491
Your EDP throttling issues are quite random. CPU-Z benchmark scores can vary a small amount even when everything is exactly the same. Whether your computer is using EDP throttling or multiplier throttling seems to happen randomly so your scores will vary based on that alone. It is possible that a sensor somewhere on your motherboard has failed and it is supplying incorrect information to the embedded controller (EC) that manages your CPU speed.
Are you using the latest BIOS version? If you are using an old version you can try updating the BIOS. If you are using the newest BIOS version, you can try using an older BIOS version. I usually do not recommend trying to update the BIOS because the latest version might disable CPU voltage control. An updated BIOS might make things worse. In this situation, your laptop is running terrible so I guess you have to try something.