It seems you don't understand the difference between strategic bombers and ground attack planes. Bombs from a strategic bomber statistically landed at least 800 meters (or something like that, I don't remember) from the point of aim. But a ground attack plane (exaggerating a little) could have inserted a bomb through a window despite a mass of anti-aircraft fire. Not without a reason, the Germans called the Il-2 flying death. And no, death chambers weren't 300 feet long and they were partially underground anyway. And prisoners of Auschwitz-Birkenau didn't leave the camp, the majority of them worked inside the camp, the others were quarantined there. And they had lots of families there. BIIb was a sector for Jewish families. BIIe was a sector for Romani families. BIIf was a hospital - directly in front of the gas chambers.