Bombing Auschwitz would have been an act of insanity for the Allies. It would have killed hundreds or thousands of prisoners and would have done nothing to shorten the war or liberate the victims of Nazi horror.
The Nazis alone are to blame for the Holocaust.
Condolences for your dad's family.
The railroads could have been taken out.
If properly done, it would have destroyed the ovens and possibly allowed many to escape. As it was the troops of the western allies were not even informed that the death camps existed, they were flabbergasted when they found them. Auschwitz was in Poland, so it may have been "liberated" by the Russians, I just don't remember.