Hong Kong - Shanghai - Doha

Hi there!

I plan to fly direct from Doha to Hong Kong for a long weekend but wanted to check the possibility of returning via Shanghai and spend a couple of days there. In order to do this, I would need to fly Doha-Hong Kong + Hong Kong-Shanghai with Cathay Pacific and then buy a separate ticket Shanghai-Doha with Qatar Airways. I would spend less than 48 hours in Shanghai, entering and leaving through Shanghai Pudong International Airport (PVG). I'm a Spanish passport holder and as far as I read my plan meets the requirements of the 72 hour free transit visa.

My questions would be:
1- Am I eligible for the 72 hour free transit if I hold confirmed tickets of 2 different airlines for the inbound and onward journeys?
2- Which of the 2 airlines should handle my free transit request? Already contacted Qatar Airways and they had no clue...

Thanks!