I'll get back on the first questions later as I've got a variety of experiences in this regard. Airline staff are the ones ordinarily best positioned to help without going way overboard. The security and passport control staff more or less want someone else to run the show and get the passenger out of there since they mostly have no idea what to do.

I'm not an Indian OCI/PIO/passport holder. I have other ways to make my life easier in India than most visitors in such circumstances and other circumstances but I don't ordinarily use them (even for such circumstances). I like to do things on my own just to see how things go sometimes. Nowadays I just have multiple entry tourist visas for India.

I applaud the OP for persisting and succeeding.