There are a few assumption implicit in your suggestions that are not valid.
1. The Philippines is a stable government that has self determination. This is obviously not true. If you look at different governments, starting with Marcos, the different governments have changed their positions from the previous government. Further, there is a big contingent of people in power that are very pro-American. Some of the behaviors of the previous governments, much like the Ukrainian or European governments, made decisions that are not in the interests of the Philippines but in the interests of America. For China to give away an island, if the next government swings back to being pro-U.S., the Chinese can't also renege and take back the island without a major loss in credibility, especially to other South East Asian nations.
Bro the assumption of a pro American is false, maybe to the intelligentsia class, who had the time to indulge in politics and dream of having a green card and working abroad BUT did the same question been ask of the worker class, the farmers or the common Tao (man). Well Duterte and BBM overwhelming victory says otherwise.
2. To gain access to Philippine ports, China must trade away its islands. this is also not true. The important thing is for China to have a very strong navy and be perceived by the Philippines as having eclipsed the U.S. The Chinese will gain all sorts of port access without having to give up an inch of ground if it is perceived as either already the top dog in the area or soon to be one.
Correct bro, Lets take Japan as an example, right now she is having nightmare with China and Russia FON practice run...lol IF become routine lets see IF Japan can stand the pressure and may seek a compromise.
3. If China does not act now, today, it will be too late. A battle will come soon that will stop the rise of China. That is simply not true as well. The U.S. have had access to the Philippines for a long time and it has always been a weak point for China. I don't foresee a military fight with China looming in the horizon because the U.S. has a lot of assets in East Asia that is also hostage to the growing Chinese military. The stronger China gets, the more likely the U.S. will lose these assets once a war with China breaks out anywhere. Losing these assets means the U.S. is finished in East Asia. No U.S. administration will cross the line with so much to lose.
Again correct bro, SCS is settle in China favor, now the target is the 2nd Island Chain and here 003, 004 and 005 carrier will play a major role. Japan will face threats from all side, the problem in her desperation she may seek US statehood to be protected...lol
My thinking to defeat the US in the Pacific you need to take out Japan first, Now if Japan economy do collapse, the US will leave because the current Japan is a dead wood, she may be the 3rd largest economy BUT her pocket of excellence is shrinking fast. The US when face with a peer competitor may seek a compromise as she rebuild, BUT she is facing two instead of one. Russia a commodity superpower and China a manufacturing juggernaut, the strategy of divided and conquer is long gone.