Yep I get it. I find Gaming is a different animal for accuracy. With gaming I feel like detecting movement early or seeing flickers of light are important for playability. Also, so many different styles with games so not sure accuracy is really possible since each game can be very abstract or devs use special filters. For Movies and such I can see it and do try to have an accurate picture there. With a movie most scenes are quick and I don’t have to move around them or look for something like on a game level. I do wish if the game supported HGIG you could set DTM to Auto and it chooses the correct setting.You are fine using Dynamic Tone Mapping ON. Purists will say the game is supposed to be that dark, but my personal preference is it's fine to give dark areas like caves and rooms without lights a little boost.
As for other gaming picture settings, lately I've discovered setting Color Gamut to "Wide" in Advanced Picture Settings. This does to color what Dynamic Tone Mapping does for black levels; it gives it a extra boost without ruining the picture. It might be "incorrect", but even so, it pleases me.
I’ll certainly try your suggestion and see how it goes. Thanks!