That doesn't look normal. It just discharges on stock and slim.
That is certainly not normal! Very weird.
As far as ROM building...If you are familiar with Linux its no too difficult,depending on the ROM. Some are problematic,but thanks to hennymcc and others who have contributed to the device trees,ROM builds can be done by others.
I have uploaded a new build for Marshmallow ROMS. I will no longer be discussing my kernel for Nougat ROMS here as it has become confusing. Just remember this kernel is end of life,so unless the zip just doesn't work (which is possible as its untested) I will not be doing anything else to this.