>Why did the gas chamber doors have hinges that turned inward when bodies would pile up against the door as people tried to force their way out of the only egress point? Why were they made of wood
Well since the Jews are on the inside of the gas chamber, and they panic and rush the doors, then they can't swing them open. That's why all exits for buildings larger than homes have doors that swing outside. Also push bars, so the force of the crowd would push them open. The Chambers were generally not made of wood.
>Why were the Russians the only ones to ever find a "death camp"
The Germans built their death camps on conquered Poland so they wouldn't have to import Jews in Germany, they wouldn't have to soil German soil with millions of dead bodies, and because it would be convenient for when they ran out of Jews and started gassing Poles. Kind of like how the United States builds it torture camps in Cuba and Iraq.
>Why did the Nazi's kill in such convoluted ways when a bullet to the brain stem costs pennies?
Gas was cheaper and faster while bullets were needed for combat. They even tried gassing by carbon monoxide poisoning from running truck engines, but zyklon B was cheaper still. However majority of Holocaust executions still involved gun-based executions by the Einsatzgruppen.
>modern crematories can't even reach a fraction of that capacity taking 2.5 hours per body and how can so many be done over a short 2 year period
Modern crematoria are designed to cremate individual bodies and return their ashes to their families, as opposed to the mass burning of large number of bodies.
Now a question to pose to Holocaust Deniers, why was no actual Nazi a Holocaust denier during and after the war?
This one simple fact shows that most of what modern deniers try to claim is a silly contrivance. From 1945 onwards, thousands of Nazis were captured and hundreds tried for their part in the Holocaust and other crimes against humanity. They tried to pretend they were someone else, they tried to pretend they didn't know what was happening, they tried to pretend they didn't have as much to do with it as others, they tried to claim they were just following orders and they tried to justify it as "the kind of thing that happens in war." But what they did NOT do was DENY it happened.
Even men on trial for their lives, in the full knowledge they would be hanged if convicted, never stood up in the courtroom and shouted "This is all a lie! This is a fabrication! There were no gas chambers and no crematoria! I'M BEING FRAMED!!!!" On the contrary, they gave great detail as to precisely how they had helped build and helped run the mechanics of mass murder, some of them even seeming proud of how they had achieved something so complex and on such a vast scale.