Why did you decide to grade in P3? Is your main target DCP for cinema? Is your monitor calibrated for P3? Why have you got several odd custom settings, such as 400 nits?
The normal way of dealing with this is having a series of nodes, as a starting point with a CST at the input and output. HDR is normally rec.2020 or HLG @600-1000nits or more. For SDR, even for most cinema DCPs Rec. 709 @100 nits is more usual and often recommended.
Have a look here, and have a look at other videos by Darren. He's a very experienced colourist and a great teacher. There is even a template for base nodes, available for download, if you sign up to his newsletter: