Well, my summary for what its worth.
Despite some gallant attempts, no-one has in my view deduced the existence of something
a priori.
I agree with those who say that nothing should not be considered as intrinsically more probable than something.
I still think that the question is ill-posed (yes, I know it's my question). The problem, as I said in the OP, is that "Why?" suggests that we are asking for an antecedent cause, which would be a thing, which would be the wrong question: like asking "Who makes it rain?", which wrongly implies that it's a person; or "How tall is jealousy?", implying that it has dimensions.
But if we can't ask "why?" then we seem in need of a whole new interrogative, such as "whub?" At which point we cease to even have the impression that we understand the question, and can be certain that we won't understand the answer.
Q: "Whub is there something rather than nothing?"
A: "Fubble."
And that would seem to be the last word on the matter.