Because of Jewish obsession with the 6 million number, no mainstream historian could ever cast doubt on the number, as Jews aggressively gatekeep such investigation and will destroy anyone who says otherwise. Seeing as how most of these historians were themselves Jewish they don't even have to threaten most of them. After the end of ww2 British intelligence estimated 4 million Jews died, and while I have no idea if that number is accurate, its one of the few unbiased estimates by people with first hand knowledge of the situation.

I listened to David Cole talk at length about the issue, and this was after he had done everything possible to get the Jewish bounty off his head removed and was trying to point out that the hardcore Holocaust denialists were wrong, and he came up with a death toll of about 3.7 million, give or take several hundred thousand. He claimed that he believes the Nazis did experiment with gas chambers in a couple of camps, but that it is extremely unlikely gas was used for mass executions at auschwitz, and there is no hard evidence of that and much evidence that contradicts it. His take seems the most objective and plausible that I've seen. He has no real reason to lie and if anything has much reason to error on the side of exaggerating the Holocaust.

A few years ago I did spend a little bit of time looking into how they arrived at the 6 million number. At the time I was generally accepting of the Holocaust narrative, including the 5-6 million number and had already heard of all the claims you just made, and I was setting out to convince alt righters to drop this holocaust denial shit, so I was expecting to see some pretty conclusive evidence. I was shocked by how little there was, despite all the usual claims that "the nazis kept meticulous records". In the end they really did have to fall back on inaccurate census claims because the nazii records wernt as precise, all encompasing and unanimous as you claim. It seemed like they basically set out to cherry pick what evidence they could find to support the preexisting 6 million claim. Obviously to retain some credibility they had to say well it could have been as low as 5.5 million, and I think it was Raul Hilberg who kind of covered their lowest acceptable numbers bases by going as low as 5.1 million. The Hilberg study was probably the most credible and extensive, and even then there were numerous glaring holes, assumptions, and leaps of logic that I immediately had questions that I never found any attempt at answering.

The Vad Yashem names list isnt reliable. It has so many duplicate names and so many people on the list were found to actually be living, and the organization itself is so biased that no intellectually honest person would give it any creedence. Which is a shame because many people on the list likely did die as a direct result of Nazi atrocities.