Related to #1, I'd also suggest stop using the phrase "should be" in respect to "earning" / "paid", at least if the goal is to reduce anxiety or plan on how to accept or change the number. If it's just complaining, though, "should" language is pretty natural and fine...
The amount you get paid is a fact. It's comparable to other facts, but the comparisons themselves are also just facts. Maybe they and other facts will help you make a case for raising it (or to your manager, a case for lowering it), but if those arguments are couched in "should" language they are probably less likely to succeed.
The amount you get paid is a fact. It's comparable to other facts, but the comparisons themselves are also just facts. Maybe they and other facts will help you make a case for raising it (or to your manager, a case for lowering it), but if those arguments are couched in "should" language they are probably less likely to succeed.