So what is your opinion (not challenging, just trying to understand) - does a pax have a legal right to decline to answer TSA questions?

I don't mean a secret 'SSI' SOP that varies with the time of day and the mood of the TSO - and can't be verified one way or the other, even in a court of law.

We've seen reports of TSA using police as sort of proxy agents. Pax refuses to submit ID to TSA for copying. TSA summons police, police demand ID, pax surrenders ID to LEO and LEO hands ID to TSA for copying and registry in federal government databases as a trouble-maker. I could, I'm guessing, decline to answer questions to an LEO - can I legally decline to answer a TSO's questions? If so, am I then legally subject to administrative fines?

TSA can (and will) share any information I give them with law enforcement - they may share the answers to questions that I would decline to answer if asked by an LEO without an attorney present.