Even if China controlls 80% of the mining power that doesn't mean that we should fear a 51% attack. Do you actually think that the guys who control mining, being Chinese or not want a 51% attack??? of course not, otherwise their investment would be worth 0....
Come the halvening, their investment will be worth 0 (unless other miners stop mining/BTC price doubles), so not that improbable :-
no, you don't know what you're talking about, after the halving miners with 0.1 cent in electricity can still mine for good profit
they are currently making 4 x($180 revenue vs $45 consumption) their consumption, in revenue....