China won't let Iran down as long as they are not doing something lethal (stupid, and I don't think they will), otherwise China would be WELL DONE (China is SO weak on energy supply) next...
hard to say.. because now is the 千載難逢 opportunity for Iran to push the Western countries away. The final goal in short term for Iran are to have both Nuclear weapon and no boycott.
It's not time for both parties... Guess who gets the good card...
US is oppressing iran to take a wrong step, but there's nothing to worry other than verbal threaten... As long as US is not inserting two battle groups in the Gulf (not including Red Sea).