When they grow up they become more and more classical so quantum entanglement disappears

I think to complete the theory one should take into account that small kids are quantum too (just try to measure their position and momentum together to check). So the |Santa> state is entangled with
the |DeepSleep> state for kids

There is a very nice example where it happens

doi.org/10.1103/Phys...

Theoretically yes. One can define the state of thermal equilibrium with density matrix \exp(-\beta H)

It is a good general rule of thumb that the people who repeat "science is political" as a self-evident mantra that requires no definition of what they mean by "science" or "political", really mean that science should be distorted to conform to THEIR politics.

Oui

It converges rapidly to the simple question “do I know the sender?”