I watched the video, but it's a little fuzzy so I had a hard time figuring out what was going on. What I see is that your track peaks at 0.0 dB before any adjustments, drops to -6.4 dB when you take off 6.4 dB via the volume slider as expected. Then you continue playback and a little further into the track, at 2:50 it goes into the red. Next, you switch the view to the master and boost both volume and gain by some amount I can't make out, and the peaks are in the red, to a value I can't make out.
I'm not seeing the mystery, sorry. Your track has peaks that exceed 0 dB, so adding anything at the master bus - by any means - is going to push it into the red, as your video shows.
Tip: play it all the way through once, then right-click on the peak indicator and select Go to Peak. This will move the Now cursor to the the highest peak in the track. This is the portion of the track you should be looping for your tests. (Part of my confusion was that in the video, you played two different portions of the track and each had different maximum peaks.)
Once you've identified the highest peak, reset all volume and gain sliders and play back that portion of the track. The peak indicator on the master bus should match that of the track. Now, to make that number go up by 1 dB, you can add 1 dB to any of the following: track volume, track gain, master gain or master volume. All four should have the same effect. To truly convince yourself that it's all working as expected, perform the test with a steady test tone, to eliminate most variables.
If all this has not just been an educational experiment and you actually just want to keep your master bus out of the red, there is but one solution: back off the gain slider on the track. That's the standard approach to mitigating an excessively hot track.