I would not be surprised if someday more than one of your first four questions are all resolved by the discovery that theoreticians have made a bad assumption,

I would not be surprised if someday more than one of your first four questions are all resolved by the discovery that theoreticians have made a bad assumption, and have been chasing today’s phlogiston or aether. This might coincide with the discovery of a new theory answering (or proving unanswerable) the fifth question as well. Or, all the necessary “fixes” to the Standard Model are out there. Either way, I agree that it might be another long wait before our technology can find meaningful new constraints.