I also would like to know what else could be done to fix this
Ah, the plot thickens... You have an H processor. XTU is only for X and K processors.
Uninstall XTU. You cannot rely upon data from a utility not intended for your processor.
Then, reset your bios, if dell allows such a thing, back to their default settiugs.
So, it never occurred to you that the problem could be with your dell or your nvidia graphics?
Since Al didn't actually say it, I will: Power Limiting, if implemented, is implemented within the BIOS.
This is a capability that laptop designers will often use to make up for the crappy batteries and/or inadequate cooling solutions that they have provided. If they've "neglected" to provide any way to configure this feature in BIOS Setup, well, it tells you what you've received. Regardless, this is between you and them.