Duterte is correct: they literally cannot afford to go to war with China. War requires two parties capable of mounting some sort of offensive or defensive combat. China sure has that, but there would be no second party stepping up to the fight.
It would take the Philippines about 20 years and 10 times their annual GDP to build up a military capable of engaging in what one might even generously call a “war” with China. And that is not economically feasible. So they literally cannot AFFORD to go to war with China, even if armed conflict were to break out.
It should would be easier for him if the US was controlling Subic Bay and Clark AFB.
How much money were US troops contributing to the local economy?