It’s one thing to say that you would rather accept the imminent possibility of your torture and death rather than stand guard at at a concentration camp; it’s quite another to do so realizing what the SS were going to do to your family and friends once you’ve gone.
How do you think Stalin got all his enemies to confess to imaginary crimes? They knew that they were condemning themselves to a death that they did not deserve, yet they would rather the world believe that they died as admitted traitors and hypocrites, just for the the chance that Stalin would have some leniency for their families. Mostly in vain, as it turned out.
Your fantasy scenario - that the SS specially sought out and conscripted Breyer and threatened his family with death if he did not work at Auschwitz is a bizarre exercise in fiction.
Breyer made the effort to get the plum position of working there.
He did it because he wanted to, because it was safer and more comfortable that serving in the Wehrmacht like the other 99% of Germans his age.