The Origin of Humour I can only answer the first question.
No. It is not a plausible theory at all. You would have to provide some solid evidence for this and I cannot see how you can.
Also, you seem to be talking about ‘laughing’ rather than humour/comedy mostly.
I think you have certainly hit on something important about storytelling. Aristotle wrote about comedy, tragedy and general performance too. Nietzsche also developed ideas on this theme. Theatre and general entertainment in the modern world is more ‘passive’ in its format. We sit and merely observe whereas if we trace back the performative arts we can see how the distinction of ‘audience’ and ‘performers’ has been a gradual development.
For example, in Shakespearean times members of the audience would actively try and attack actors playing villains because the line between ‘real’ and ‘performance’ was not like today. Today at the theatre no one would take a murder scene to be an actual murder. If go back further, or look at different cultures, there are instances where the ‘performance’ is something that ‘audience members’ actively participate in - they take on the role of some character in a trance-like fashion.
As for humour in general there is certainly a common theme of ‘surprise’ and, as Aristotle put it, viewing comedy as something bad happening to someone deserving of the bad element, whereas tragedy is something bad happening to someone perceived as ‘good’ - in simplistic terms. Sympathetic feelings play into the humour, or lack of, as well as simple surprise/shock.
People in high emotional states of suffering will often laugh. People have many different reactions to many situations.
I don’t see how it makes any sense to suggest that physical exhaustion is a precursor to laughter. We do know that hyperventilation can induce certain states, and that physical exertion can create a certain high. In what you are saying there is a very tenuous link at best.