Yeah this m3 pro isn't really doing 1600 nits. Marginally brighter than my 2012.

To get to actual 1600 nits you need to use scripts.

https://github.com/SerjoschDuering/macbook_1600nits

Not sure the impacts to display health or battery running the screen full bore like this.

I use Lunar and have used it on my Pro Display XDR and every MBP with XDR I've owned with 0 issues.