I did a quick test to see how much color was left. as long as your example is a worst case scenario, you shouldn't even need to use channel mixer.
Note: if your levels are clipped, it means that your color channels are clipped as well (which means it might be easier for you to visually see levels aligned up with RGB parade than creating a grey composite color in the histogram) ; although you still will be able to use HSL scopes for middle grey white balance.
here's a histogram balancing example in premiere with HSL scopes
here's a rgb parade balancing example in resolve
I'd also look up skin tone line on vectorscopes,.
resolve skin tone line
and using color chart plugins that can often be a single click