Yes, on graduate students at places like CERN, whose careers live or die based on the probabilistic detection of a single particle during their time "in the box".

Yes. If you do a diffraction experiment where a particle scatters off a lattice of atoms, but leaves no trace of which atom it interacted with, then you see a diffraction pattern that corresponds to the superposition of all the possibilities. If you do a modified experiment where the particle leaves one atom in a different state, then you see a different result, which corresponds to scattering off of just one atom, not the whole lattice.

It doesn't matter whether you actually go and check on the atom, though. What matters is whether there's something you could check on.

There's nothing to test.

The elements of the experiment are each well understood and defined, but adding them together you link two incompatible ways of looking at the world. The thought experiment puts it on you to reconcile that.

That would be pretty interesting. I dunno, maybe put an egg in there instead of the poison vial, creating a superposed system of intact egg/cracked egg instead?